libstdc++ Hastable: Move std::is_permutation to limit includes

libstdc++ Hastable: Move std::is_permutation to limit includes

Move std::is_permutation algorithm with associated helpers to stl_algobase.h
to remove stl_algo.h include from hashtable_policy.h and so reduce preprocess
size of unordered_map and unordered_set headers.

	* include/bits/stl_algo.h
	(__find_if, __count_if, __is_permutation, std::is_permutation): Move...
	* include/bits/stl_algobase.h: ...here.
	* include/bits/hashtable_policy.h: Remove <bits/stl_algo.h> include.