Add C intrinsics for Intel SHA Extensions

Intrinsics added shaintrin.h, which is included from x86intrin.h if __SHA__ is
enabled. SHA implies SSE2, which is needed for the __m128i type.

Also add the -msha/-mno-sha option.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190999 91177308-0d34-0410-b5e6-96231b3b80d8