Save skin names in save files instead of skin numbers

See merge request STJr/SRB2!1503

[SUGOI] Level select no longer assumes that games will always be linear

See merge request STJr/SRB2!1492

[SUGOI] Make stagefailed more useful, add linedef executor to toggle, and expose to Lua

Closes #361

See merge request STJr/SRB2!1463

[SUGOI] Remove skin->availability, add SECRET_SKIN

See merge request STJr/SRB2!1474

Fix slope plane rotation and alignment (resolves #508)

Closes #508

See merge request STJr/SRB2!1464

Fix some compiler warnings

See merge request !1504

Check against null tmpusher source before attempting to push a thing.

See merge request !1413

tRNS chunk fix

See merge request !1393

Optimize Picture_GetPatchPixel

See merge request !1342

Remove music slot compatibility

See merge request STJr/SRB2!1321

Scale minimum dashmode thok speed on actionspd, not normalspeed

See merge request !1311

Set the target of a spawned ghost to where it came from.

Closes #517

See merge request !1358

Make steam apply sprung flag

See merge request !1365

Don't apply pw_justlaunched if the player didn't actually launch off a slope

See merge request !1447

No fire shield palflash (resolves #512)

Closes #512

See merge request !1473

Change Raspberry's chat colormap to V_ROSYMAP

See merge request !1441

Add more actions for slope copying

See merge request STJr/SRB2!1406

Add linedef specials for multitagging in binary maps

See merge request !1485

The year is 2021

See merge request !1500

Some of these integers exceed the precision of float. In
that case the number is rounded. The rounding shouldn't
matter too much anyway, so just shut the compiler up.

Add some comments, write an empty string instead of a boolean determining if the bot skin exists or not.

I was a little scared of doing this at first, but after a bit of thought & some testing that it'll be fine.

Allows you to save a game as any character, and you don't have to load the files in a specific order to access the save file.

Fix a series of buffer overflows in SOC (primarily Character section) loading

See merge request !1457

arccosine Lua exposure

See merge request !1455

[SUGOI] Allow setting sound captions in SOC

See merge request !1469

Monster cleaning up again

See merge request !1433

Load netgame error fixes

See merge request !1482

Polyobject over 3D floor fix for software renderer

See merge request STJr/SRB2!1488