c++config (_GLIBCXX14_USE_CONSTEXPR): New.

c++config (_GLIBCXX14_USE_CONSTEXPR): New.

2016-05-24  François Dumont  <fdumont@gcc.gnu.org>

	* include/bits/c++config (_GLIBCXX14_USE_CONSTEXPR): New.
	* include/bits/hashtable_policy.h
	(_Prime_rehash_policy::__has_load_factor): New. Mark rehash policy
	having load factor management.
	(_Mask_range_hashing): New.
	(__clp2): New.
	(_Power2_rehash_policy): New.
	(_Inserts<>): Remove last template parameter, _Unique_keys, so that
	partial specializations only depend on whether iterators are constant
	or not.
	* testsuite/23_containers/unordered_set/hash_policy/26132.cc: Adapt to
	test new hash policy.
	* testsuite/23_containers/unordered_set/hash_policy/load_factor.cc:
	Likewise.
	* testsuite/23_containers/unordered_set/hash_policy/rehash.cc:
	Likewise.
	* testsuite/23_containers/unordered_set/insert/hash_policy.cc:
	Likewise.
	* testsuite/23_containers/unordered_set/max_load_factor/robustness.cc:
	Likewise.
	* testsuite/23_containers/unordered_set/hash_policy/power2_rehash.cc:
	New.
	* testsuite/performance/23_containers/insert/54075.cc: Add benchmark
	using the new hash policy.
	* testsuite/performance/23_containers/insert_erase/41975.cc: Likewise.

From-SVN: r236669