Blending changes

See merge request STJr/SRB2!1446

Fix CTF flag patch garbage (resolves #506)

Closes #506

See merge request STJr/SRB2!1453

Fix dedicated server crashing when exiting special stage (Fixes #453)

Closes #453

See merge request STJr/SRB2!1451

Fix a OpenGL backend DeleteTexture crash (Fixes #499)

Closes #499

See merge request STJr/SRB2!1448

BRUH MOMENT

Fix jet fume crash when dashmode is above DASHMODE_MAX

See merge request STJr/SRB2!1450

I would like to use higher dashmode values for extra leniency, the jet fume kicks and screams when this happens.

Let uppercase letters thru dedicated console

See merge request STJr/SRB2!1449

don't HWR_ClearAllTextures() in software (fixes #389)

Closes #389

See merge request STJr/SRB2!1440

Smoother freelook in Software

See merge request STJr/SRB2!1444

Do not let SF_NOJUMPSPIN characters enter sectors they could not enter if standing at full height (Closes #457)

Closes #457

See merge request STJr/SRB2!1432

Prevent a single client from blocking Lua file transfers

See merge request STJr/SRB2!1435

Our menu system sucks. That's all I have to say.

See merge request STJr/SRB2!1445

Floorsprite fixes

See merge request STJr/SRB2!1443

Mhm hmm...

This changes how blend modes render, and includes fixes.

This fixes the texture of the floorsprite sometimes facing the wrong way, since plane rendering can change the view angle.

Fix addons with custom gamedata not loading

Closes #473

See merge request STJr/SRB2!1427

Fix unused variable warning when USE_APNG is not defined

See merge request STJr/SRB2!1343

- PF_NOJUMPDAMAGE no longer affects height at all (you're welcome katsy).
- Characters with SF_NOJUMPSPIN will only use spinheight when panim is PA_ROLL. They cannot enter gaps when jumping with spinheight, unless also spinning or gliding.
- All other characters use spinheight when panim is PA_JUMP or PA_ROLL. They can enter gaps when jumping with spinheight.