Sound system startup fix

Closes #281

See merge request STJr/SRB2Internal!465

The letter

See merge request STJr/SRB2Internal!438

Sprite rotation (resolves #183)

Closes #183

See merge request STJr/SRB2Internal!430

Write empty file on clearbans

See merge request STJr/SRB2Internal!464

Merge branch 'rotsprite_i' of https://git.magicalgirl.moe/STJr/SRB2Internal.git into rotsprite_toast

* Remove the 22(!!) NiGHTS sprite2s that no longer get used in ROTSPRITE builds (which should be our main builds going forward).
* Rename `SPR2_NGT0` to `SPR2_NFLY`, and `SPR2_DRL0` to `SPR2_NDRL` to account for this. (requires modifying player.dta)

Other things I missed. Also added SF_NONIGHTSROTATION. Do I even have to keep the old behaviour? I have no idea.

Resolve #281. (Might have problems with non-SDL interfaces, but definitely good for what we're shipping with.)

(Why doesn't it work for I_Quit?)

Stop the clock!

See merge request STJr/SRB2Internal!450

MP Charsel menu fixes

See merge request STJr/SRB2Internal!457

Skin UsabLua

See merge request STJr/SRB2Internal!458

Radio Mode fixes

See merge request STJr/SRB2Internal!459

Update libs (revert revert revert buffalo buffalo buffalo)

See merge request STJr/SRB2Internal!436

New map command

See merge request STJr/SRB2Internal!424

Update SFX definition to credit VAdaPEGA specifically, given we've made most credits more specific now too.

* Prevent (extremely unlikely) wraparound of patch frame calculation for the epynomous Radio (sigsegv prevention).
* Use thinstring for Authors field on the screen.

Radio mode

See merge request STJr/SRB2Internal!443

(This means you don't need quoting.)

GFZ3's boss hangs when dodging

See merge request STJr/SRB2Internal!403

Azure Temple Zone hazards, round 2

See merge request STJr/SRB2Internal!437

Metal battle, recording, and playback improvements

Closes #283 and #215

See merge request STJr/SRB2Internal!431

# Conflicts:
#	src/p_user.c

Internal MD3 merge 2 good riddance glBegin

See merge request STJr/SRB2Internal!362

Texture flat optimization

Closes #257

See merge request STJr/SRB2Internal!405