Clang changes to support LLVM removal of runtime multithreading
support (llvm revision r210600).

Reviewers: rnk

Differential Revision: http://reviews.llvm.org/D4077

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210601 91177308-0d34-0410-b5e6-96231b3b80d8