Revert "Revert "Merge to upstream r304942.""

This reverts commit 38a0d5af7e.

Test: make checkbuild
Test: ./run_tests.py
Test: ./run_tests.py --bitness 64

test/std/utilities/template.bitset/bitset.hash/bitset.pass.cpp

@@ -30,6 +30,8 @@ test()
     typedef std::hash<T> H;
     static_assert((std::is_same<typename H::argument_type, T>::value), "" );
     static_assert((std::is_same<typename H::result_type, std::size_t>::value), "" );
+    ASSERT_NOEXCEPT(H()(T()));
+
     H h;
     T bs(static_cast<unsigned long long>(N));
     const std::size_t result = h(bs);