clang-cl: support -v

It doesn't conflict with any cl.exe options and it's useful for debugging.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201597 91177308-0d34-0410-b5e6-96231b3b80d8
Updated documentation for Thread Safety Analysis.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201598 91177308-0d34-0410-b5e6-96231b3b80d8