Attempt two at fixing threading on Windows
Attempt two at fixing threading on Windows

Reviewers: compnerd

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D28735

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@292027 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx