Support for C1x _Atomic specifier (see testcase).  This is primarily being committed at the moment to help support C++0x <atomic>, but it should be a solid base for implementing the full specification of C1x _Atomic.

Thanks to Jeffrey Yasskin for the thorough review!



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@141330 91177308-0d34-0410-b5e6-96231b3b80d8
39 files changed