Add reduce_*_ep[i|u][8|16] series intrinsics

gcc/ChangeLog:

	* config/i386/avx2intrin.h
	(_MM_REDUCE_OPERATOR_BASIC_EPI16): New macro.
	(_MM_REDUCE_OPERATOR_MAX_MIN_EP16): Ditto.
	(_MM256_REDUCE_OPERATOR_BASIC_EPI16): Ditto.
	(_MM256_REDUCE_OPERATOR_MAX_MIN_EP16): Ditto.
	(_MM_REDUCE_OPERATOR_BASIC_EPI8): Ditto.
	(_MM_REDUCE_OPERATOR_MAX_MIN_EP8): Ditto.
	(_MM256_REDUCE_OPERATOR_BASIC_EPI8): Ditto.
	(_MM256_REDUCE_OPERATOR_MAX_MIN_EP8): Ditto.
	(_mm_reduce_add_epi16): New instrinsics.
	(_mm_reduce_mul_epi16): Ditto.
	(_mm_reduce_and_epi16): Ditto.
	(_mm_reduce_or_epi16): Ditto.
	(_mm_reduce_max_epi16): Ditto.
	(_mm_reduce_max_epu16): Ditto.
	(_mm_reduce_min_epi16): Ditto.
	(_mm_reduce_min_epu16): Ditto.
	(_mm256_reduce_add_epi16): Ditto.
	(_mm256_reduce_mul_epi16): Ditto.
	(_mm256_reduce_and_epi16): Ditto.
	(_mm256_reduce_or_epi16): Ditto.
	(_mm256_reduce_max_epi16): Ditto.
	(_mm256_reduce_max_epu16): Ditto.
	(_mm256_reduce_min_epi16): Ditto.
	(_mm256_reduce_min_epu16): Ditto.
	(_mm_reduce_add_epi8): Ditto.
	(_mm_reduce_mul_epi8): Ditto.
	(_mm_reduce_and_epi8): Ditto.
	(_mm_reduce_or_epi8): Ditto.
	(_mm_reduce_max_epi8): Ditto.
	(_mm_reduce_max_epu8): Ditto.
	(_mm_reduce_min_epi8): Ditto.
	(_mm_reduce_min_epu8): Ditto.
	(_mm256_reduce_add_epi8): Ditto.
	(_mm256_reduce_mul_epi8): Ditto.
	(_mm256_reduce_and_epi8): Ditto.
	(_mm256_reduce_or_epi8): Ditto.
	(_mm256_reduce_max_epi8): Ditto.
	(_mm256_reduce_max_epu8): Ditto.
	(_mm256_reduce_min_epi8): Ditto.
	(_mm256_reduce_min_epu8): Ditto.
	* config/i386/avx512vlbwintrin.h:
	(_mm_mask_reduce_add_epi16): Ditto.
	(_mm_mask_reduce_mul_epi16): Ditto.
	(_mm_mask_reduce_and_epi16): Ditto.
	(_mm_mask_reduce_or_epi16): Ditto.
	(_mm_mask_reduce_max_epi16): Ditto.
	(_mm_mask_reduce_max_epu16): Ditto.
	(_mm_mask_reduce_min_epi16): Ditto.
	(_mm_mask_reduce_min_epu16): Ditto.
	(_mm256_mask_reduce_add_epi16): Ditto.
	(_mm256_mask_reduce_mul_epi16): Ditto.
	(_mm256_mask_reduce_and_epi16): Ditto.
	(_mm256_mask_reduce_or_epi16): Ditto.
	(_mm256_mask_reduce_max_epi16): Ditto.
	(_mm256_mask_reduce_max_epu16): Ditto.
	(_mm256_mask_reduce_min_epi16): Ditto.
	(_mm256_mask_reduce_min_epu16): Ditto.
	(_mm_mask_reduce_add_epi8): Ditto.
	(_mm_mask_reduce_mul_epi8): Ditto.
	(_mm_mask_reduce_and_epi8): Ditto.
	(_mm_mask_reduce_or_epi8): Ditto.
	(_mm_mask_reduce_max_epi8): Ditto.
	(_mm_mask_reduce_max_epu8): Ditto.
	(_mm_mask_reduce_min_epi8): Ditto.
	(_mm_mask_reduce_min_epu8): Ditto.
	(_mm256_mask_reduce_add_epi8): Ditto.
	(_mm256_mask_reduce_mul_epi8): Ditto.
	(_mm256_mask_reduce_and_epi8): Ditto.
	(_mm256_mask_reduce_or_epi8): Ditto.
	(_mm256_mask_reduce_max_epi8): Ditto.
	(_mm256_mask_reduce_max_epu8): Ditto.
	(_mm256_mask_reduce_min_epi8): Ditto.
	(_mm256_mask_reduce_min_epu8): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/avx512vlbw-reduce-op-1.c: New test.