Clang 5.0 implements these changes here: 87cd035326
MSVC++ will implement these changes in the first toolset update to 2017.
Differential Revision: https://reviews.llvm.org/D33021
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@302710 91177308-0d34-0410-b5e6-96231b3b80d8