Merge new string builtin

This adds the new builtin 'string' which supports various string
manipulation and matching algorithms, including PCRE based regular
expressions.

Fixes #2296

Squashed commit of the following:

commit 4c3eaeb6e57d76463e9683c327142b0aeafb92b8
Author: ridiculousfish <corydoras@ridiculousfish.com>
Date:   Sat Sep 12 12:51:30 2015 -0700

    Remove testdata and doc dirs from pcre2 source

commit b2a8b4b50f2398b204fb72cfe4b5ba77ece2e1ab
Merge: 11c8a47 7974aab
Author: ridiculousfish <corydoras@ridiculousfish.com>
Date:   Sat Sep 12 12:32:40 2015 -0700

    Merge branch 'string' of git://github.com/msteed/fish-shell into string-test

commit 7974aab6d367f999f1140ab34c2535cef5cf3b00
Author: Michael Steed <msteed@saltstack.com>
Date:   Fri Sep 11 13:00:02 2015 -0600

    build pcre2 lib only, no docs

commit eb20b43d2d96b7e6d24618158ce71078de83c40b
Merge: 1a09e70 5f519cb
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Sep 10 20:00:47 2015 -0600

    Merge branch 'string' of github.com:msteed/fish-shell into string

commit 1a09e709d028393c9e9e6dc9a84278f399a15f3d
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Sep 10 19:58:24 2015 -0600

    rebase on master & address the fallout

commit a0ec9772cd1a0a548a501a7633be05dab4e5ee46
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Sep 10 19:26:45 2015 -0600

    use fish's wildcard_match() for glob matching

commit 64c25a01e3f7234f220ba13545cf658a7492b1a4
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Aug 27 08:19:23 2015 -0600

    some fixes from review

    - string_get_arg_stdin(): simplify and don't discard the argument when
      the trailing newline is absent
    - fix calls to pcre2 for e.g. string match -r -a 'a*' 'b'
    - correct test for args coming from stdin

commit ece7f35ec5f4093763627d68d671b6c0c876896d
Author: Michael Steed <msteed68@gmail.com>
Date:   Sat Aug 22 19:35:56 2015 -0600

    fixes from review

    - Makefile.in: restore iwyu target
    - regex_replacer_t::replace_matches(): correct size passed to realloc()

commit 9ff7477a926c4572e26171cab3cd42f8086be678
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Aug 20 13:08:33 2015 -0600

    Minor doc improvements

commit baf4e096b22dde3063b85b833795eb570d660ba7
Author: Michael Steed <msteed68@gmail.com>
Date:   Wed Aug 19 18:29:02 2015 -0600

    another attempt to fix the ci build

commit 896a2c2b279a419747bea26102229fbe84534a6f
Author: Michael Steed <msteed68@gmail.com>
Date:   Wed Aug 19 18:03:49 2015 -0600

    Updates after review comments

    - make match/replace without -a operate on the first match on each
      argument
    - use different exit codes for "no operation performed" and errors, as
      grep does
    - refactor regex compile code
    - use human-friendly error messages from pcre2
    - improve error handling & reporting elsewhere
    - add a few tests
    - make some doc fixes
    - some simplification & cleanup
    - fix ci build failure (I hope)

commit efd47dcbda2ca247d58bee56a7774cd75a1062fd
Author: Michael Steed <msteed68@gmail.com>
Date:   Wed Aug 12 00:26:07 2015 -0600

    fix dependencies for parallel make

commit ed0850e2db467362066a3d94e3ececd17c1756cd
Author: Michael Steed <msteed68@gmail.com>
Date:   Tue Aug 11 23:37:22 2015 -0600

    Add missing pcre2 files + .gitignore

commit 9492e7a7e929c03554336be1ddf80ca6b37f53c5
Author: Michael Steed <msteed68@gmail.com>
Date:   Tue Aug 11 22:44:05 2015 -0600

    add pcre2-10.20 and update license.hdr

commit 1a60b933718feb20c0bf7c9e257b8e495014ea1b
Author: Michael Steed <msteed68@gmail.com>
Date:   Tue Aug 11 22:41:19 2015 -0600

    add string builtin files

    - string builtin source, tests, & docs
    - changes to configure.ac & Makefile.in

commit 5f519cb2a2c05213e0a88a7add7af288bc1c1352
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Sep 10 19:26:45 2015 -0600

    use fish's wildcard_match() for glob matching

commit 2ecd24f79500879e2de5bdf1b4c19dd44fc6ac85
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Aug 27 08:19:23 2015 -0600

    some fixes from review

    - string_get_arg_stdin(): simplify and don't discard the argument when
      the trailing newline is absent
    - fix calls to pcre2 for e.g. string match -r -a 'a*' 'b'
    - correct test for args coming from stdin

commit 45b777e4dc85c05cd4a186f4bdcae543c21aaf08
Author: Michael Steed <msteed68@gmail.com>
Date:   Sat Aug 22 19:35:56 2015 -0600

    fixes from review

    - Makefile.in: restore iwyu target
    - regex_replacer_t::replace_matches(): correct size passed to realloc()

commit 981cbb6ddf742a5fe8881af916e7b870b7e6422a
Author: Michael Steed <msteed68@gmail.com>
Date:   Thu Aug 20 13:08:33 2015 -0600

    Minor doc improvements

commit ddb6a2a8fdb6aa31aad41e80d5481bb32c6ed8ff
Author: Michael Steed <msteed68@gmail.com>
Date:   Wed Aug 19 18:29:02 2015 -0600

    another attempt to fix the ci build

commit 1e34e3191b028162863d263e9868052f75194aa5
Author: Michael Steed <msteed68@gmail.com>
Date:   Wed Aug 19 18:03:49 2015 -0600

    Updates after review comments

    - make match/replace without -a operate on the first match on each
      argument
    - use different exit codes for "no operation performed" and errors, as
      grep does
    - refactor regex compile code
    - use human-friendly error messages from pcre2
    - improve error handling & reporting elsewhere
    - add a few tests
    - make some doc fixes
    - some simplification & cleanup
    - fix ci build failure (I hope)

commit 34232e152df17a3cfbf0a094dd51d148a4f04e6f
Author: Michael Steed <msteed68@gmail.com>
Date:   Wed Aug 12 00:26:07 2015 -0600

    fix dependencies for parallel make

commit 00d7e781697f53454beb91c1d0fc4b2d28d6e034
Author: Michael Steed <msteed68@gmail.com>
Date:   Tue Aug 11 23:37:22 2015 -0600

    Add missing pcre2 files + .gitignore

commit 4498aa5f576e09634f7f619443e74d2f33c108e4
Author: Michael Steed <msteed68@gmail.com>
Date:   Tue Aug 11 22:44:05 2015 -0600

    add pcre2-10.20 and update license.hdr

commit 290c58c72e22db644ccf6fa9088051644980ed0a
Author: Michael Steed <msteed68@gmail.com>
Date:   Tue Aug 11 22:41:19 2015 -0600

    add string builtin files

    - string builtin source, tests, & docs
    - changes to configure.ac & Makefile.in

1 files changed, 309 insertions, 0 deletions

diff --git a/pcre2-10.20/src/pcre2_error.c b/pcre2-10.20/src/pcre2_error.c
new file mode 100644
index 00000000..c539bd23
--- /dev/null
+++ b/pcre2-10.20/src/pcre2_error.c
@@ -0,0 +1,309 @@
+/*************************************************
+*      Perl-Compatible Regular Expressions       *
+*************************************************/
+
+/* PCRE is a library of functions to support regular expressions whose syntax
+and semantics are as close as possible to those of the Perl 5 language.
+
+                       Written by Philip Hazel
+     Original API code Copyright (c) 1997-2012 University of Cambridge
+         New API code Copyright (c) 2015 University of Cambridge
+
+-----------------------------------------------------------------------------
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright notice,
+      this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the name of the University of Cambridge nor the names of its
+      contributors may be used to endorse or promote products derived from
+      this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+-----------------------------------------------------------------------------
+*/
+
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "pcre2_internal.h"
+
+#define STRING(a)  # a
+#define XSTRING(s) STRING(s)
+
+/* The texts of compile-time error messages. Compile-time error numbers start
+at COMPILE_ERROR_BASE (100).
+
+Do not ever re-use any error number, because they are documented. Always add a
+new error instead. This used to be a table of strings, but in order to reduce
+the number of relocations needed when a shared library is loaded dynamically,
+it is now one long string. We cannot use a table of offsets, because the
+lengths of inserts such as XSTRING(MAX_NAME_SIZE) are not known. Instead,
+pcre2_get_error_message() counts through to the one it wants - this isn't a
+performance issue because these strings are used only when there is an error.
+
+Each substring ends with \0 to insert a null character. This includes the final
+substring, so that the whole string ends with \0\0, which can be detected when
+counting through. */
+
+static const char compile_error_texts[] =
+  "no error\0"
+  "\\ at end of pattern\0"
+  "\\c at end of pattern\0"
+  "unrecognized character follows \\\0"
+  "numbers out of order in {} quantifier\0"
+  /* 5 */
+  "number too big in {} quantifier\0"
+  "missing terminating ] for character class\0"
+  "invalid escape sequence in character class\0"
+  "range out of order in character class\0"
+  "quantifier does not follow a repeatable item\0"
+  /* 10 */
+  "internal error: unexpected repeat\0"
+  "unrecognized character after (? or (?-\0"
+  "POSIX named classes are supported only within a class\0"
+  "POSIX collating elements are not supported\0"
+  "missing closing parenthesis\0"
+  /* 15 */
+  "reference to non-existent subpattern\0"
+  "pattern passed as NULL\0"
+  "unrecognised compile-time option bit(s)\0"
+  "missing ) after (?# comment\0"
+  "parentheses are too deeply nested\0"
+  /* 20 */
+  "regular expression is too large\0"
+  "failed to allocate heap memory\0"
+  "unmatched closing parenthesis\0"
+  "internal error: code overflow\0"
+  "unrecognized character after (?<\0"
+  /* 25 */
+  "lookbehind assertion is not fixed length\0"
+  "malformed number or name after (?(\0"
+  "conditional group contains more than two branches\0"
+  "assertion expected after (?( or (?(?C)\0"
+  "(?R or (?[+-]digits must be followed by )\0"
+  /* 30 */
+  "unknown POSIX class name\0"
+  "internal error in pcre2_study(): should not occur\0"
+  "this version of PCRE2 does not have Unicode support\0"
+  "parentheses are too deeply nested (stack check)\0"
+  "character code point value in \\x{} or \\o{} is too large\0"
+  /* 35 */
+  "invalid condition (?(0)\0"
+  "\\C is not allowed in a lookbehind assertion\0"
+  "PCRE does not support \\L, \\l, \\N{name}, \\U, or \\u\0"
+  "number after (?C is greater than 255\0"
+  "closing parenthesis for (?C expected\0"
+  /* 40 */
+  "recursion could loop indefinitely\0"
+  "unrecognized character after (?P\0"
+  "syntax error in subpattern name (missing terminator)\0"
+  "two named subpatterns have the same name (PCRE2_DUPNAMES not set)\0"
+  "group name must start with a non-digit\0"
+  /* 45 */
+  "this version of PCRE2 does not have support for \\P, \\p, or \\X\0"
+  "malformed \\P or \\p sequence\0"
+  "unknown property name after \\P or \\p\0"
+  "subpattern name is too long (maximum " XSTRING(MAX_NAME_SIZE) " characters)\0"
+  "too many named subpatterns (maximum " XSTRING(MAX_NAME_COUNT) ")\0"
+  /* 50 */
+  "invalid range in character class\0"
+  "octal value is greater than \\377 in 8-bit non-UTF-8 mode\0"
+  "internal error: overran compiling workspace\0"
+  "internal error: previously-checked referenced subpattern not found\0"
+  "DEFINE group contains more than one branch\0"
+  /* 55 */
+  "missing opening brace after \\o\0"
+  "internal error: unknown newline setting\0"
+  "\\g is not followed by a braced, angle-bracketed, or quoted name/number or by a plain number\0"
+  "a numbered reference must not be zero\0"
+  "an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)\0"
+  /* 60 */
+  "(*VERB) not recognized or malformed\0"
+  "number is too big\0"
+  "subpattern name expected\0"
+  "digit expected after (?+\0"
+  "non-octal character in \\o{} (closing brace missing?)\0"
+  /* 65 */
+  "different names for subpatterns of the same number are not allowed\0"
+  "(*MARK) must have an argument\0"
+  "non-hex character in \\x{} (closing brace missing?)\0"
+#ifndef EBCDIC
+  "\\c must be followed by a printable ASCII character\0"
+#else
+  "\\c must be followed by a letter or one of [\\]^_?\0"
+#endif
+  "\\k is not followed by a braced, angle-bracketed, or quoted name\0"
+  /* 70 */
+  "internal error: unknown opcode in find_fixedlength()\0"
+  "\\N is not supported in a class\0"
+  "too many forward references\0"
+  "disallowed Unicode code point (>= 0xd800 && <= 0xdfff)\0"
+  "using UTF is disabled by the application\0"
+  /* 75 */
+  "using UCP is disabled by the application\0"
+  "name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)\0"
+  "character code point value in \\u.... sequence is too large\0"
+  "digits missing in \\x{} or \\o{}\0"
+  "syntax error in (?(VERSION condition\0"
+  /* 80 */
+  "internal error: unknown opcode in auto_possessify()\0"
+  "missing terminating delimiter for callout with string argument\0"
+  "unrecognized string delimiter follows (?C\0"
+  "using \\C is disabled by the application\0"
+  "(?| and/or (?J: or (?x: parentheses are too deeply nested\0"
+  ;
+
+/* Match-time and UTF error texts are in the same format. */
+
+static const char match_error_texts[] =
+  "no error\0"
+  "no match\0"
+  "partial match\0"
+  "UTF-8 error: 1 byte missing at end\0"
+  "UTF-8 error: 2 bytes missing at end\0"
+  /* 5 */
+  "UTF-8 error: 3 bytes missing at end\0"
+  "UTF-8 error: 4 bytes missing at end\0"
+  "UTF-8 error: 5 bytes missing at end\0"
+  "UTF-8 error: byte 2 top bits not 0x80\0"
+  "UTF-8 error: byte 3 top bits not 0x80\0"
+  /* 10 */
+  "UTF-8 error: byte 4 top bits not 0x80\0"
+  "UTF-8 error: byte 5 top bits not 0x80\0"
+  "UTF-8 error: byte 6 top bits not 0x80\0"
+  "UTF-8 error: 5-byte character is not allowed (RFC 3629)\0"
+  "UTF-8 error: 6-byte character is not allowed (RFC 3629)\0"
+  /* 15 */
+  "UTF-8 error: code points greater than 0x10ffff are not defined\0"
+  "UTF-8 error: code points 0xd800-0xdfff are not defined\0"
+  "UTF-8 error: overlong 2-byte sequence\0"
+  "UTF-8 error: overlong 3-byte sequence\0"
+  "UTF-8 error: overlong 4-byte sequence\0"
+  /* 20 */
+  "UTF-8 error: overlong 5-byte sequence\0"
+  "UTF-8 error: overlong 6-byte sequence\0"
+  "UTF-8 error: isolated 0x80 byte\0"
+  "UTF-8 error: illegal byte (0xfe or 0xff)\0"
+  "UTF-16 error: missing low surrogate at end\0"
+  /* 25 */
+  "UTF-16 error: invalid low surrogate\0"
+  "UTF-16 error: isolated low surrogate\0"
+  "UTF-32 error: code points 0xd800-0xdfff are not defined\0"
+  "UTF-32 error: code points greater than 0x10ffff are not defined\0"
+  "bad data value\0"
+  /* 30 */
+  "patterns do not all use the same character tables\0"
+  "magic number missing\0"
+  "pattern compiled in wrong mode: 8/16/32-bit error\0"
+  "bad offset value\0"
+  "bad option value\0"
+  /* 35 */
+  "invalid replacement string\0"
+  "bad offset into UTF string\0"
+  "callout error code\0"              /* Never returned by PCRE2 itself */
+  "invalid data in workspace for DFA restart\0"
+  "too much recursion for DFA matching\0"
+  /* 40 */
+  "backreference condition or recursion test is not supported for DFA matching\0"
+  "function is not supported for DFA matching\0"
+  "pattern contains an item that is not supported for DFA matching\0"
+  "workspace size exceeded in DFA matching\0"
+  "internal error - pattern overwritten?\0"
+  /* 45 */
+  "bad JIT option\0"
+  "JIT stack limit reached\0"
+  "match limit exceeded\0"
+  "no more memory\0"
+  "unknown substring\0"
+  /* 50 */
+  "non-unique substring name\0"
+  "NULL argument passed\0"
+  "nested recursion at the same subject position\0"
+  "recursion limit exceeded\0"
+  "requested value is not available\0"
+  "requested value is not set\0"
+  ;
+
+
+/*************************************************
+*            Return error message                *
+*************************************************/
+
+/* This function copies an error message into a buffer whose units are of an
+appropriate width. Error numbers are positive for compile-time errors, and
+negative for match-time errors (except for UTF errors), but the numbers are all
+distinct.
+
+Arguments:
+  enumber       error number
+  buffer        where to put the message (zero terminated)
+  size          size of the buffer
+
+Returns:        length of message if all is well
+                negative on error
+*/
+
+PCRE2_EXP_DEFN int PCRE2_CALL_CONVENTION
+pcre2_get_error_message(int enumber, PCRE2_UCHAR *buffer, size_t size)
+{
+char xbuff[128];
+const char *message;
+size_t i;
+uint32_t n;
+
+if (size == 0) return PCRE2_ERROR_NOMEMORY;
+
+if (enumber > COMPILE_ERROR_BASE)  /* Compile error */
+  {
+  message = compile_error_texts;
+  n = enumber - COMPILE_ERROR_BASE;
+  }
+else                               /* Match or UTF error */
+  {
+  message = match_error_texts;
+  n = -enumber;
+  }
+
+for (; n > 0; n--)
+  {
+  while (*message++ != CHAR_NULL) {};
+  if (*message == CHAR_NULL)
+    {
+    sprintf(xbuff, "No text for error %d", enumber);
+    break;
+    }
+  }
+
+for (i = 0; *message != 0; i++)
+  {
+  if (i >= size - 1)
+    {
+    buffer[i] = 0;     /* Terminate partial message */
+    return PCRE2_ERROR_NOMEMORY;
+    }
+  buffer[i] = *message++;
+  }
+
+buffer[i] = 0;
+return i;
+}
+
+/* End of pcre2_error.c */