X86: add more GATHER intrinsics in Clang

Corrected type for index of _mm256_mask_i32gather_pd
  from 256-bit to 128-bit
Corrected types for src|dst|mask of _mm256_mask_i64gather_ps
  from 256-bit to 128-bit

Support the following intrinsics:
  _mm_mask_i32gather_epi64, _mm256_mask_i32gather_epi64,
  _mm_mask_i64gather_epi64, _mm256_mask_i64gather_epi64,
  _mm_mask_i32gather_epi32, _mm256_mask_i32gather_epi32,
  _mm_mask_i64gather_epi32, _mm256_mask_i64gather_epi32

llvm-svn: 159403