Define AVX conversion intrinsics
Define AVX conversion intrinsics

This defines the following intrinsics:

 * `_mm256_cvtepi32_pd`
 * `_mm256_cvtepi32_ps`
 * `_mm256_cvtpd_epi32`
 * `_mm256_cvtpd_ps`
 * `_mm256_cvtps_epi32`
 * `_mm256_cvtps_pd`
 * `_mm256_cvttpd_epi32`
 * `_mm256_cvttps_epi32`

Intel reference: https://software.intel.com/en-us/node/514130.

GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust