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/function.objects/unord.hash/floating.pass.cpp

@@ -24,6 +24,8 @@
 #include <limits>
 #include <cmath>
 
+#include "test_macros.h"
+
 template <class T>
 void
 test()
@@ -31,6 +33,7 @@ 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;
 
     std::size_t t0 = h(0.);