4x-6x faster on sandybridge
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

This provides a fallback when building with Yasm enabled, but neither
inline assembly, nor the _mm_empty intrinsic are available or enabled.
Signed-off-by: Diego Biurrun <diego@biurrun.de>

This allows detecting CPU features with builds that have neither
gcc inline assembly nor the right compiler intrinsics enabled.

Move vector_fmul() from DSPContext to AVFloatDSPContext.