type specific code into the appropriate files (which will later be merged as
much as possible) and remove all model type specific code from model.c.
gl_model.c is no more as it ended up being an exact copy of model.c minus a
header include and a prototype, neither of which were needed.
convert #if USE_INTEL_ASM to #ifdef USE_INTEL_ASM
add cl_math.S to math_ASM
unfortunatly, snd_mixa.o isn't being built. Haven't figured that one out yet