Added the opencl.ocl.version metadata to be emitted with amdgcn. Created a static function emitOCLVerMD which is shared between triple spir and target amdgcn.
Also added new testcases to existing test file, spir_version.cl inside test/CodeGenOpenCL.
Patch by Aaron En Ye Shi.
Differential Revision: https://reviews.llvm.org/D22424
llvm-svn: 276010