SVN r6381: N64 driver

I ported over all of angrylion et al's fixes from their MESS-derived plugin. Things look considerably better blending-wise, but unfortunately, texture seam issues remain. frown

Some noteworthy improvements:

MAME now runs in MESS via the N64 driver:

Mario 64's trees, shadows, and decal textures look much, much better thanks to the perfect Z handling:

Likewise, Mario's textures are finally correct thanks to the updated Color Combiner and Blender handling: