Apple was not including poll.h despite needing it.

These were not defined for macOS despite being necessary.

Delete old and unused rendering-related code

See merge request STJr/SRB2!2341

Fix various segfaults caused by missing P_MobjWasRemoved checks

See merge request STJr/SRB2!2052

Rendering cvars that control rendering walls, floors, and things.

See merge request STJr/SRB2!1526

Load TRNSLATE files from folders

Closes #1206

See merge request STJr/SRB2!2370

Fix credit sequence not compensating for non-green resolutions

Closes #1184

See merge request STJr/SRB2!2320

Fix insane TTY input latency

See merge request STJr/SRB2!2360

Change MAXSKINS from 256 to 255

See merge request STJr/SRB2!2365

Tokenizer mem

See merge request STJr/SRB2!2363

A value of -1 is sometimes reserved for "no skin", leaving 255 other values for skin numbers

Do not alllow error codepaths of UPnP to leave the mutex locked

Closes #1200

See merge request STJr/SRB2!2349

Issue #1150 - Fix it the right way!

See merge request STJr/SRB2!2350

This reverts merge request !2334

Merge remote-tracking branch 'origin/1200-next-cannot-load-game-when-using-srb2-launcher' into 1200-next-cannot-load-game-when-using-srb2-launcher

Fix tint equation shader

See merge request STJr/SRB2!2348

Print UPnP status to log file/external console only

See merge request STJr/SRB2!2347

Delete outdated docs

See merge request STJr/SRB2!2346

Add UDMF specification document

See merge request STJr/SRB2!2345

Cutscene timing fixed

See merge request STJr/SRB2!2344

Fix FreeBSD memory reporting if built with cmake

See merge request STJr/SRB2!2314

I don't think It's not really important enough that it's worth always notifying the user about it.