Explicitly set GLSL shader versions.
Basic camera controls.
WASD for forward/back and strafe left/right.
Space/shift for flying up/down, ctrl increases horizontal speed.
Mouse movement controls yaw (horizontal) and pitch (vertical) angles.
Add NBT decoder.
Implement simple loading of Anvil region files and chunks within.
[WIP] render some minecraft stuff
Temporary workaround to get the SDL2 backend to compile.