Fix incorrect offsets of cached rotsprites

See merge request STJr/SRB2Internal!468

Paper sign tweaks

See merge request STJr/SRB2Internal!460

Flickies not in walls

See merge request STJr/SRB2Internal!461

Improved title screen flashes

See merge request STJr/SRB2Internal!462

LJ saved me from self destruction by bad code

See merge request STJr/SRB2Internal!463

Allow item respawn in co-op again

See merge request STJr/SRB2Internal!466

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)

Why was it even disabled anyway.

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.)

Disable menu input on the title screen for the first second (ie, before the flash), to guarantee people won't start the menu the very first tic after the fade and ruin the animation. (Console and gif/screenshot recording still works, for the impatient.)

(Why doesn't it work for I_Quit?)

I'm a dumbass who makes extremely consequential typoes (and since the typo is no longer in effect, the supergold can be brightened some more)

https://cdn.discordapp.com/attachments/244035368595357697/644316971738857483/srb20060.gif

https://cdn.discordapp.com/attachments/428262628893261828/644295409283497995/srb20058.gif

* Make the white flash a little easier on the eyes by putting the full-screen fade behind the title wing/ring, then drawing multiple overlaid colormapped versions of them on top of each other.
* Darken the pre-flash screen.

* Add a "moveforward" param to P_InternalFlickySpawn, which controls whether to spawn the flicky a little in front or behind of the object making it.
* Expose this via additional upper-16-bits flags of A_FlickySpawn.
* Use this to make Snailers not spawn their flicky inside the wall they're attached to.
* Make the behaviour of Egg Capsules more consistent mechanically regarding the flicky spawning, using the above as one relevant element.

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