functional_hash.h (std::__is_fast_hash<>): New.

2013-02-04  François Dumont  <fdumont@gcc.gnu.org>

	* include/bits/functional_hash.h (std::__is_fast_hash<>): New.
	* include/bits/basic_string.h: Specialize previous to mark
	std::hash for string types as slow.
	* include/bits/hashtable.h (__cache_default): Replace is_integral
	with __is_fast_hash.
	* src/c++11/hash_c++0x.cc: Add type_traits include.
	* testsuite/23_containers/unordered_set/instantiation_neg.cc:
	Adapt dg-error line number.
	* testsuite/23_containers/unordered_set/
	not_default_constructible_hash_neg.cc: Likewise.

From-SVN: r195738