libc++: Add some missing #includes to atomics tests. libc++ doesn't need these
at the moment, but they allow these tests to be used to test clang against
libstdc++. Add myself to the credits file, as suggested by Howard.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@155085 91177308-0d34-0410-b5e6-96231b3b80d8
26 files changed