Another C++14 feature.

        * include/bits/stl_algo.h (is_permutation): Add overloads from N3671.
        * include/bits/stl_algobase.h (equal, mismatch): Likewise.
        * testsuite/25_algorithms/equal/1.cc: Remove duplicate test case.
        * testsuite/25_algorithms/equal/2.cc: New.
        * testsuite/25_algorithms/equal/check_type2.cc: New.
        * testsuite/25_algorithms/is_permutationqual/2.cc: New.
        * testsuite/25_algorithms/is_permutationqual/check_type2.cc: New.
        * testsuite/25_algorithms/mismatch/2.cc: New.
        * testsuite/25_algorithms/mismatch/check_type2.cc: New.
        * testsuite/util/testsuite_iterators.h: Fix spelling.

Tested x86_64-linux, committed to trunk.