Semi-hacky fix to R_AddSpriteDefs printing `Added -1 frames in 0 sprites`: if the start marker is equal to or beyond the end marker, none of r_things' `for (l = startlump; l < endlump; l++)` loops will run, so just assume no sprites.

Simply put, `W_CheckNumForFolderStartPK3` and its `End` equivalent will never return INT16_MAX for nonexistence, and I don't want to break any assumptions elsewhere by modifying those functions directly, so this is the simplest possible fix.

Boss Scream fix

See merge request STJr/SRB2Internal!581

Fix intro's BRITEGG/DARKEGG scale

See merge request STJr/SRB2Internal!580

Clean up music error messages

Closes #407

See merge request STJr/SRB2Internal!585

Jumphood

See merge request STJr/SRB2Internal!573

Restore spindash sounds to DSSPNDSH

See merge request STJr/SRB2Internal!579

Brakyeet2

See merge request STJr/SRB2Internal!578

This Black Eggman? ***YEET*** (resolves #399)

Closes #399

See merge request STJr/SRB2Internal!575

Gold statue MTF_EXTRA

See merge request STJr/SRB2Internal!576

Discovered this was wrong when working on the config for brakyeet, MS objected to the hack so he's updating the tutorial map accordingly.

Deton alert sound

See merge request STJr/SRB2Internal!491

S&T no flip

See merge request STJr/SRB2Internal!571

The final countdown (resolves #400).

Closes #400

See merge request STJr/SRB2Internal!574

Intermission Buffer Clear On Map Command (no funny name today)

See merge request STJr/SRB2Internal!570

New intro graphics

See merge request STJr/SRB2Internal!524

Flag return completion (resolve #396).

Closes #396

See merge request STJr/SRB2Internal!572

Edit config to account for new behaviour (plus add gold mode for the Eggman Statue, which I forgot to add earlier).

Resolve issue #399 in the silliest way possible: by having Brak be yeeted off the platform by an explosion at his feet, preventing the downed mech from being anywhere near the escape pod.

Endelinger (resolves #384).

Closes #384

See merge request STJr/SRB2Internal!569

Sleepwalkin (resolves most of #382)

Closes #382

See merge request STJr/SRB2Internal!567