x86inc: Rename "program_name" to "private_prefix"

The new name is more descriptive and will allow defining a separate
public prefix for externally visible library symbols.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
x86inc: Add cvisible macro for C functions with public prefix

This allows defining externally visible library symbols.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
x86: Add a Yasm-based emms() replacement

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>