This patch cleans up a number of issues reported by STL, including:
1) Fix duplicate is_convertible test.
2) Move non-standard reference_wrapper tests under test/libcxx
3) Fix assumption that sizeof(wchar_t) == 32 in the codecvt and
wstring_convert tests.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@302870 91177308-0d34-0410-b5e6-96231b3b80d8
Testing the concrete implementation of INVOKE means calling the implementation
specific names `__invoke` and `__invoke_constexpr`. For this reason the test
are non-standard. For this reason it's best if the tests live outside of the
`test/std` directory.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@267973 91177308-0d34-0410-b5e6-96231b3b80d8
