commit
For testing the new iteration, the texture cache disk download was written
into the main thread instead of into the separate threads. Now they're back
in separate threads again.
Also I think some of these files probably should have been in the previous
commit.
Once again, conceptually this system should work, however it does not seem to
be the most efficient and it wouldn't surprise me if the multithreading was
eventually upgraded to an even more coherent system one day. However for
"core principles" this should be fairly decent.
The previous iteration was fairly OpenGL-heavy. It's now been separated into
a base class that is OpenGL independent and a derived class that is
OpenGL-based. Over time this should allow for portability away from OpenGL
if necessary.