* Store the number of frames per sprite2 run in the spr2frames struct.
* Reintroduce P_GetModelSprite2, to allow for the sprite2 defaulting system to be used to full advantage even in GL.
* Instead of splitting the SUPER and normal SPR2 stuff within the same cell of the struct, have them exist in different cells just like in the "normal" sprite2 structs.
* Allow for just providing spr2 frames in order without specifying which "normal" sprite2 frame it's supposed to replace.
Also:
* Fix FF_VERTICALFLIP-ignoring regression.
* Fix whitespace adjustment in win_dll.c
* Remove bracket in P_GetSkinSprite2 because I realised it was extraneous while making sure P_GetModelSprite2 worked with it.
Also:
* SPR2_XTRA - instead of defining lumpnames in S_SKIN, those kinds of assets can just be bundled into the spriteset. Required for ending cutscene stuff, I guess, but also done for HUD life icon and character select image (aside from Sonic&Tails, still SOC'd in).
* Minor oversights in SPR2 support corrected.
* Better evaluation, featuring ending assets.
* Intro has warping-in blackrock, reusing ending assets.
* Cutscene text now supports lowercase (intro and custom).
* Disable the asset-fucking "gamma correction" I put in over two years ago when implementing colour cube. (This is the only thing I could move into another branch if you MUST, but it's basically invisble in the diff so w/e.)
* Don't blank the screen if the top left pixel of a screen-covering patch is transparent. (Checked via nonzero topdelta for first column)
Bugs:
* OPENGL ONLY: The first ~20 frames of both endings are fucked. A little help here? Might be HWR_DrawFadeFill's fault, which I just created. OR it could be in f_finale, but I doubt it, since it doesn't appear in Software.
