Add include guards to prfchwintrin.h.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181513 91177308-0d34-0410-b5e6-96231b3b80d8
xopintrin.h: Add wrappers for all flavors of _mm_com.

GCC defines only the wrappers, MSVC defines both, we define both now too.
PR15844.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181514 91177308-0d34-0410-b5e6-96231b3b80d8