Automatically insert emms after running each MMX test
Automatically insert emms after running each MMX test

After using MMX intrinsics the FPU must be
cleared by using _mm_empty() before interfacing
with any x87 code.

This commit makes the simd_test macro automatically do that
when one of the features enabled is "mmx".

rust-lang/stdarch,rust-lang/stdarch,rust-lang/stdarch,rust-lang/stdarch,rust-lang/stdarch