Rasterization Improvements (Patreon)

I'm implementing an indexing system for handling the selection of drawing modes for both rigid surfaces and liquid surfaces. This will make it easier to implement more drawing modes. There are a few bugs to sort out, but it should be fully working soon.

The rasterization code for liquids went through a big cleanup, and while doing that I also removed the code to skip perspective correction on the lighting of liquids. That code was a hack I had done to improve the framerate of lit liquids, but it would inevitably cause glitches on lit liquids in non-horizontal planes (waterfalls, etc).

I have plans to optimize the perspective correction a lot more in the future, so that hack wouldn't be needed anyway.

The version 0.6.2 should be ready after the drawing mode indexing bugs are fixed.