gl, sw and sw32 use blend palettes, so share the code. This also abandons
the optimization for transforming verts in sw (had all sorts of problems
anyway). sw still doesn't work, though.
There are still many issues to sort out, but the basics are working.
Problems:
rendered fullbright (no lighting done)
normals are ignored
extra textures (glow etc) not used/loaded
4 models on the screen don't seem to be a problem.
