Occlusion plane system

[sauraen]

This PR adds an occlusion plane management system, which is always enabled when F3DEX3 is enabled.

Occlusion plane candidates can be specified on a per-room basis, exported by fast64. This system runs once per frame, attempts to choose the best candidate from the available options using a bunch of heuristics, computes the F3DEX3 occlusion plane coefficients for that plane, and sends them to the RSP.

If in auto mode, it switches between base and NOC microcodes based on whether any occlusion plane candidates exist (effectively changes up to once per room transition). This also means that NOC will be used for vanilla scenes or for romhacks which don't use occlusion planes.

The system also uploads a modified version of the occlusion plane before the skybox is rendered, which is able to occlude sky triangles occluded by the scene. With this system and @Thar0 's changes to not clear the framebuffer before drawing the sky, the user must ensure that any occluding scene geometry is drawn with RA, not AA, rendermodes. If AA is used, graphical artifacts may occur along the edges of scene tris, as they will be drawing directly over an old framebuffer with possible partial coverage. The user must also ensure that the player cannot move the camera beyond the occluding scene geometry, or else the player will be able to see through the hole to past framebuffers, causing massive visual glitches. If these conditions cannot be met, the user should remove the code involving skyPlane in occlusionplanes.c.