Add a flag -fthread-sanitizer.

This flag enables ThreadSanitizer instrumentation committed to llvm as r150423.
The patch includes one test for -fthread-sanitizer and one similar test for -faddress-sanitizer.
This patch does not modify the linker flags (as we do it for -faddress-sanitizer) because the run-time library is not yet
committed and it's structure in compiler-rt is not 100% clear.
The users manual wil be changed in a separate commit.

llvm-svn: 151846