Implemented SPR model lighting, and added a menu option for it. No support for Darkplaces’ naming convention of lit SPR models yet though.

Some code cleanup, and some more work on the new tinting system.

I’ve also optimized the translucent SPR model drawing code, and found out that translucent SPR models seems to also be suffering from the same bug as translucent BSP models. I’m going to remove the optimizations to see if that solves the problem.