Update to latest llvm/clang
Update to latest LLVM
Fix Visual Studio lookup logic to handle Visual Studio 2012 and 2013 (11.0 and 12.0)
Modify Visual Studio lookup logic to prioritize environment variables over registry
Add new option Gnu99Mode in ParserOptions, passes -std=gnu99 to clang instead of c++ parameters
Fix NRE (when parsing C code in gnu99 mode)