Coqmktop without Sys.command, changes in ./configure -*byteflags options

NB: Please re-run ./configure after pulling this commit

 For launching ocamlc/ocamlopt, coqmktop doesn't use Sys.command anymore,
 but rather CUnix.sys_command, which is based on Unix.create_process.
 This way, we do not need to bother with the underlying shell
 (/bin/sh or cmd.exe) and the way arguments are to be quoted :-).
 Btw, many cleanups of coqmktop.

 Only difficulty: the -coqrunbyteflags of ./configure is a "meta-option"
 that collect as a string several sub-options to be given by coqmktop to ocamlc.
 For instance ./configure -coqrunbyteflags "-dllib -lcoqrun". We need now to
 parse all these sub-options. To ease that, I've made the following changes
 to the ./configure options:

 * The -coqrunbyteflags and its blank-separated argument isn't accepted
   anymore, and is replaced by a new option -vmbyteflags which expects
   a comma-separated argument. For instance:

   ./configure -vmbyteflags "-dllib,-lcoqrun"

   Btw, on this example, the double-quotes aren't mandatory anymore :-)

 * The -coqtoolsbyteflags isn't accepted anymore. To the best of my
   knowledge, nobody ever used it directly (it was internally triggered
   as a byproduct of the -custom option). The only interest I can think of
   for this option was to cancel the default use of ocamlc custom-linking
   on Win32 and MacOS. For that, ./configure now provides a -no-custom option.

1 files changed, 3 insertions, 3 deletions

diff --git a/myocamlbuild.ml b/myocamlbuild.ml
index 5669dccab..6d3a24306 100644
--- a/myocamlbuild.ml
+++ b/myocamlbuild.ml
@@ -259,9 +259,9 @@ let extra_rules () = begin
        let lines = List.map (fun s -> s^"\n") lines in
        let line0 = "\n(* Adapted variables for ocamlbuild *)\n" in
        (* TODO : line2 isn't completely accurate with respect to ./configure:
-	  the case of -local -coqrunbyteflags foo isn't supported *)
+	  the case of -local -vmbyteflags foo isn't supported *)
        let line1 =
-	 "let coqrunbyteflags = \"-dllib -lcoqrun\"\n"
+	 "let vmbyteflags = [\"-dllib\";\"-lcoqrun\"]\n"
        in
        Echo (lines @ (if local then [line0;line1] else []),
 	     "coq_config.ml"));
@@ -316,7 +316,7 @@ let extra_rules () = begin
   flag ["compile"; "c"] cflags;
   dep ["ocaml"; "use_libcoqrun"; "compile"] [libcoqrun];
   dep ["ocaml"; "use_libcoqrun"; "link"; "native"] [libcoqrun];
-  flag ["ocaml"; "use_libcoqrun"; "link"; "byte"] (Sh Coq_config.coqrunbyteflags);
+  flag ["ocaml"; "use_libcoqrun"; "link"; "byte"] (Sh Coq_config.vmbyteflags);
 
   (* we need to use a different ocamlc. For now we copy the rule *)
   if w32 then