Handle endianness with the pre-processor, and consistantly

Merged Dylan Baker requested to merge dbaker/mesa:endian-macros into master

This little series is taken out of my earlier utils reworks series, but only covers using the preprocessor for endianness. this replaces run-time detection of endianness with compile-time detection, and makes it all much more uniform. This is all handled in the utils helper library instead of through core mesa.

Merge request reports