We no longer have to maintain this standard manually. I actually suggest making booster sectors use the lightlevel of their surrounding sectors so that only the booster itself glows.
(OGL support is commented out, since it conflicts with sal-lighting and should probably be done there)
"precipprops" lets you create a new precipitation type by picking a mobj type to use, how many random states it has, and flags for effects such as thunder/lightning. Seesound on the mobj type sets an ambient sound (like rain drops) and mass sets the sound's frequency in tics. This could open up the possibility for SOC/Lua Weather options later.
I've tried to make this so it almost never under-compensates, and over-compensates very little where possible.
I don't think it's 1:1 to software's current behaviour, and probably never will be due to software being very strange.
* Ranges between full brightness to half-brightness (50% of fullbright effect).
* Has both software and GL support (I think - GL needs to be doublechecked, but I think it's just GL being murky in general).
* Used by Rings.
* Backport FF_GLOBALANIM and FF_RANDOMANIM extensions to FF_ANIMATE from 2.2.
* Rings use the former instead of their own hacky solution to the problem.
* Also backport FF_VERTICALFLIP, because why not.
* Inverts sprite relative to gravity. I remember wanting this for the flipped death sprite for Jawz, but then Oni drew his own frame for that, so it doesn't matter.
* Refactor vissprite struct a tad, given I did so in internal where I pulled most of these improvements from.
* Should be no in-game affect; let me know if you notice any regressions.
No longer using byte2float in DrawPolygon -- use the surface color data directly
Vertex Buffer Objects for non-interpolated model frames
Removed some old unused paletted texture stuff
Needs to be tested in gravity flip
Also flips the normal on linedef based slopes so that it's facing the correct direction
Also makes it so slopelaunch doesn't always remove the standingslope (going down some slopes would cause it to be constantly unset and reset)
