Hybrid Skyboxes Done (Patreon)

The version 0.3.2 is ready for release, but my ISP is offline. In the worst case, I'll upload it through my smartphone later.

The hybrid skybox code is much cleaner than before. There's a bit of optimization, the top vertices will be adjusted to reduce the amount of overdraw on the sides. Still no texel coordinates concatenation, but the performance is lightweight enough for now.

A new cvar r_skybox_overdraw was introduced to control sky polygon behavior. If it's enabled, sky brushes will still occlude other geometry when skyboxes are enabled, and the world geometry will be rendered in a second pass. If it's disabled, sky brushes will be ignored by the renderer and the skybox will be rendered in the same pass as the rest of the world. To put it simple, r_skybox_overdraw 0 is much faster but will be glitchy in a few maps, while r_skybox_overdraw 1 always renders perfectly but is a lot slower. It's disabled by default.