LLVM2.2 x64 JIT trouble on VStudio build

Hello, Evan

I think a Win64 version of X86CompilationCallback{2} is still needed. Also, it's not clear to me how to force a non-Windows CC. It may require some FE extension to support it?

Well, as currently we don't have windows64 support in FE correct
(non-windows) CC will be set automatically.