[OpenCL] Add ocl and spir version for spir target

Summary: Add opencl.spir.version and opencl.ocl.version metadata for CodeGen to identify OpenCL version. 

Reviewers: yaxunl, Anastasia

Subscribers: cfe-commits, pekka.jaaskelainen

Differential Revision: http://reviews.llvm.org/D17596

llvm-svn: 264241