[PowerPC] [Clang] Port SSE4.1-compatible insert intrinsics

This patch adds three intrinsics compatible to x86's SSE 4.1 on PowerPC
target, with tests:

- _mm_insert_epi8
- _mm_insert_epi32
- _mm_insert_epi64

The intrinsics implementation is contributed by Paul Clarke.

Reviewed By: jsji

Differential Revision: https://reviews.llvm.org/D89242