Many surfaces are missing (I suspect it's due to transform stage
management in the index emitter), and currently only the light maps are
rendered (still not binding the correct textures), but the basics are
working.
Copying data from the wrong buffer was the cause of the corrupted brush
model vertices, and then lots of little errors (mostly forgetting to
multiply by bpp) for textures.
I had originally planned on mixing the stage management with general
texture support code like I did in glsl, but I think that was a mistake
and I did keep looking for scrap.[ch] when I wanted to edit something to
do with the scrap...
There's still a problem with the vertex data itself not getting sent to
the GPU properly, but vulkan is now happy with my tiny test map (which
required disabling skies entirely until I get null textures working).
