Savegame hotfixes
Yes, this another netgame related fix! Named this "savegame hotfixes" rather than "ERCZ hotfix" or the like in advance of the fact we probably need a general branch for other $$$.sav fixes?
Anyway, fixes included in by this branch:
* ERCZ's lava falls now act as expected rather than being stuck in place for the map's duration, fixing all other known desynchronisation issues known in the map for the time being (yay)
* Changing sector tags in a map no longer causes joiners to netgames to have their SRB2 application stop responding etc
* Player names should no longer turn red in the console in gametypes outside of CTF/Team Match if a resynch occurs (not $$$.sav related, but it's related to netplay so I lumped it in anyway)
See merge request !150
Some texture-related fixes
Bugs fixed in this branch:
* upper/lower/middle textures with non-existent texture ids being capable of crashing the game. For instance, RVZ1 has colormap codes on non-colormap linedefs, which causes them to wind up with invalid texture ids because of how the game tries to interpret lower/upper textures with "#" followed by characters on normal linedefs. Fortunately these "textures" are normally not visible anyway (since they're all in control sectors) unless they are swapped with in-level textures by some crazy Lua script of some sort...
* animated single-patch textures with holes displaying garbage on first viewing (see this thread: https://mb.srb2.org/showthread.php?t=42195)
* the heights of the lighting (shadows or colormapping) from water/translucent/shadowcasting/etc FOFs become messed up when displayed on repeated midtextures.
See merge request !144
Dunno who thought it was a good idea to lump tag, nexttag and firsttag together in $$$.sav, but that meant changing sector tags caused SRB2 to stop responding since it lead to the tag lists being broken
These functions were already here before, and I /swear/ the slope
physics became slightly less glitchy after switching to them...
Only issue is the slope plane mapping code hasn't been properly
converted yet, so they don't render properly for now.
