1. Improve performance by coalescing multiple surfaces/draw calls with
the same textures (within a single brush model).
2. Add lightmaps. We don't support lightstyles yet, though, so they seem
a bit wrong at times. Also gamma handling is not great.
Oh well.
it's now *very slow* because every surface (which is just a few polys)
gets its own draw call and descriptor bind. F
we also had to make default sampler repeating, so now 2d textures in
menu have weird edge artifacts. also F
making progress i guess
Ivan Avdeev