Export of internal Abseil changes.

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1c1d6e2404dfc6caa022b335df5acdac6da50fe1 by Derek Mauro <dmauro@google.com>:

Fix the internal namespacing in unaligned_access.h

PiperOrigin-RevId: 215434506

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17d4400aebf025a230690fc1c7a968ef8d85bbba by Eric Fiselier <ericwf@google.com>:

gtest depends on the GCC extension allowing variadic macros
to be passed a empty parameter pack for ..., but LLVM diagnoses
this as a GNU extension.

This patch suppresses the warning when building the absl tests.

PiperOrigin-RevId: 215426161

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f2c49dde23a9f445b9de963f1bbe840ebb568b30 by Eric Fiselier <ericwf@google.com>:

Use EXPECT_DEATH_IF_SUPPORTED instead of EXPECT_DEATH.

This avoids breaking the test when gtest doesn't support
death tests.

PiperOrigin-RevId: 215423849

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cd687c1e121709603f4fc3726b534f6a9c52cc89 by Eric Fiselier <ericwf@google.com>:

Disable LLVM's -Wmissing-variable-declarations in tests.

GCC's configuration already disables this via -Wno-missing-declarations,
this change makes LLVM do the same.

The warning would otherwise flag most tests which use ABSL_FLAG.

PiperOrigin-RevId: 215407429

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d14098824c84e3a8c8f6fb920e0335fb48fe2010 by Eric Fiselier <ericwf@google.com>:

Fix local variable shadowing in city hash implementation.

PiperOrigin-RevId: 215407249

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4b5e140ba743f0d231790a26c49083abb4329e2c by Abseil Team <absl-team@google.com>:

Make raw_hash_set::reserve 2X fast when reserve doesn't do any allocation.
Make raw_hash_set::reserve ~1% faster when reserve does some (128~4k) allocation.

PiperOrigin-RevId: 215348727

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461161e65e04b801480aa117af2534c594654ccf by Eric Fiselier <ericwf@google.com>:

Internal change

PiperOrigin-RevId: 215272283

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50413ae31ad3d3a177257416acd8ede47a17bff2 by Eric Fiselier <ericwf@google.com>:

Internal Change

PiperOrigin-RevId: 215233183

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477be54c43d61019a8fe4e190e340eb52737d383 by Abseil Team <absl-team@google.com>:

Clarify misleading comment on ABSL_ATTRIBUTE_UNUSED

PiperOrigin-RevId: 215185496

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2cafa2b5287507d3a946682aee9ab13af6d471c9 by Matt Kulukundis <kfm@google.com>:

Add support for absl::Hash to various absl in types.

PiperOrigin-RevId: 215039569

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082248901991aa3d29be0ea3689c7f213cf0fd83 by Derek Mauro <dmauro@google.com>:

Remove an instance of HAS_GLOBAL_STRING from hash_function_defaults.h

PiperOrigin-RevId: 214989094

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b929f61907f0786a6133e3a9d7287e339c0a0acb by Derek Mauro <dmauro@google.com>:

Internal import of Github #174
Fix code snippet in comment
https://github.com/abseil/abseil-cpp/pull/174

PiperOrigin-RevId: 214958849

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f2c5e829eca11c352e121f56eefbf87083305023 by Derek Mauro <dmauro@google.com>:

Internal import of GitHub #173
Fix CMake build for absl::container.
https://github.com/abseil/abseil-cpp/pull/173

PiperOrigin-RevId: 214957796

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d704f860f9fddafb99e34e6c5032e49f73874e10 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 214828181
GitOrigin-RevId: 1c1d6e2404dfc6caa022b335df5acdac6da50fe1
Change-Id: I551de2b1ba0cbaf6856cd5959358cf6651179dea

3 files changed, 10 insertions, 0 deletions

diff --git a/absl/types/BUILD.bazel b/absl/types/BUILD.bazel
index 7841a97..32f690c 100644
--- a/absl/types/BUILD.bazel
+++ b/absl/types/BUILD.bazel
@@ -136,6 +136,7 @@ cc_test(
         "//absl/base:exception_testing",
         "//absl/container:fixed_array",
         "//absl/container:inlined_vector",
+        "//absl/hash:hash_testing",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
     ],
@@ -153,6 +154,7 @@ cc_test(
         "//absl/base:exception_testing",
         "//absl/container:fixed_array",
         "//absl/container:inlined_vector",
+        "//absl/hash:hash_testing",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
     ],
diff --git a/absl/types/span.h b/absl/types/span.h
index 3359ce5..911af0c 100644
--- a/absl/types/span.h
+++ b/absl/types/span.h
@@ -485,6 +485,13 @@ class Span {
                : (base_internal::ThrowStdOutOfRange("pos > size()"), Span());
   }
 
+  // Support for absl::Hash.
+  template <typename H>
+  friend H AbslHashValue(H h, Span v) {
+    return H::combine(H::combine_contiguous(std::move(h), v.data(), v.size()),
+                      v.size());
+  }
+
  private:
   pointer ptr_;
   size_type len_;
diff --git a/absl/types/span_test.cc b/absl/types/span_test.cc
index fbce7e8..bd739ff 100644
--- a/absl/types/span_test.cc
+++ b/absl/types/span_test.cc
@@ -29,6 +29,7 @@
 #include "absl/base/internal/exception_testing.h"
 #include "absl/container/fixed_array.h"
 #include "absl/container/inlined_vector.h"
+#include "absl/hash/hash_testing.h"
 #include "absl/strings/str_cat.h"
 
 namespace {