[Upstream] Handle sample image types.

https://github.com/intel/llvm/pull/1945 and https://github.com/intel/llvm/commit/f9520e69ba88c1e11adcb7be92ac0aa46ed72e5c added new built-in types, which are used in DPC++ library headers.

We should upstream this patch to llorg to enable parsing of DPC++ headers.

This issue blocks https://github.com/intel/llvm/milestone/1. To unblock this milestone we could guard sampled image types uses in DPC++ with pre-process for compilers w/o sampled image types support.