Do lightlist height stepping *after* the heights are used by the FOF rendering code, not before (yes, I caught that they remove a heightstep beforehand for FOFs, but that wasn't done for midtextures it seems?)

Additionally add some macros for repeated slope end assignments and overflow tests

Move shared code here instead of duplicating it for both dc_numlights and non-dc_numlights rendering code

Also added a few comments, and include the out of range check in the "shared code" above

Tiny fix so that joystick2 being closed can let the JoystickSubSystem close before game close.

See merge request STJr/SRB2!292

No memory leak here, just a very tiny thing I noticed.

Free SOC_s to a good home

See merge request STJr/SRB2!291

* Fix a memory leak regarding implementation of SOC_ (improperly copypasted code from LUA_LoadLump!!)
* Optimise the repeated strlen usage into a single call, which is stored for later.

Dr. Who And The Sleeping Weather

See merge request STJr/SRB2!288

SP savegame continues icon crash

See merge request STJr/SRB2!290

Makefile: Split zlib and libpng

See merge request STJr/SRB2!285

Fixer mixer: Mixer Memory Leaks

See merge request STJr/SRB2!287

Weather is already run client-side. What if we ran it render-side, for major performance gains? This commit will answer all your questions - and more!

A value of 1 in freesrc for Mix_LoadWAV_RW and Mix_LoadMus_RW calls SDL_RWclose on the RWops anyway.
For Mix_LoadWAV_RW the RWops is freed right after the data is loaded (because it makes a copy of the data in memory)
For Mix_LoadMUS_RW the RWops is freed when Mix_FreeMusic is called (because the data is not a copy)
So setting 1 on freesrc doesn't actually free the RWops immediately on Mix_LoadMus_RW *unless* it failed to load any music.

Mix_QuickLoad_RAW sets a flag in the Mix_Chunk so that Mix_FreeChunk doesn't actually Free the sound.
Checks for the flag when freeing, and if it's 0, we free the data manually after Mix_FreeChunk.
I went back to Z_Malloc and Z_Free for this because they still work after this.

Use MemAvailable instead

See merge request STJr/SRB2!281

Thanks again MonsterIestyn!

Colormap code cleanup

See merge request STJr/SRB2!275

R_CreateColormap2 and R_MakeColormaps have been made obsolete, it's just R_CreateColormap now, like it used to be!

With that, I moved R_CreateColormap2's exclusive software colormap malloc code to R_CreateColormap, and merged the two software-only blocks of code into one. I also disabled any unneeded variables and fixed a preprocessor-related goofup

Fix for HOM removal in non-green resolutions

See merge request STJr/SRB2!273

Yo Screen So Wide y Is Invalid

See merge request STJr/SRB2!271

v_video Killed The r_radio Star

See merge request STJr/SRB2!270

Zalloc Potter and the Death-Free Hallows

See merge request STJr/SRB2!269