Silencing a signed vs unsigned comparison mismatch in MSVC.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183837 91177308-0d34-0410-b5e6-96231b3b80d8
Fix buildbot breakage on PPC64.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183847 91177308-0d34-0410-b5e6-96231b3b80d8