Hash: Fix int128 with BOOST_HASH_NO_EXTENSIONS.

I don't think int128 should count as an extension.

BOOST_HASH_NO_EXTENSIONS is actually a bit of a pain, and I don't think it's
that useful. Maybe I should deprecate it.

[SVN r81870]

doc/changes.qbk

@@ -142,6 +142,9 @@
 [h2 Boost 1.52.0]
 
 * Restore `enum` support, which was accidentally removed in the last version.
+* Add support for `boost::int128_type` and `boost::uint128_type` where
+  available - currently only `__int128` and `unsigned __int128` on some
+  versions of gcc.
 * New floating point hasher - will hash the binary representation on more
   platforms, which should be faster.
 * On platforms that are known to have standard floating point, don't use the

include/boost/functional/hash/hash.hpp

@@ -439,6 +439,11 @@ namespace boost
     BOOST_HASH_SPECIALIZE(boost::ulong_long_type)
 #endif
 
+#if defined(BOOST_HAS_INT128)
+    BOOST_HASH_SPECIALIZE(boost::int128_type)
+    BOOST_HASH_SPECIALIZE(boost::uint128_type)
+#endif
+
 #if !defined(BOOST_NO_CXX11_HDR_TYPEINDEX)
     BOOST_HASH_SPECIALIZE(std::type_index)
 #endif