Make a few messages more helpful (resolves #485)

Closes #485

See merge request STJr/SRB2!1519

Rollout rock improvements

Closes #445, #221, and #532

See merge request STJr/SRB2!1401

Make Armageddon Shield instantly kill Egg Guards (Closes #225)

Closes #225

See merge request STJr/SRB2!1378

Allow sliders passage through spin gaps (resolves #576)

Closes #576

See merge request STJr/SRB2!1520

Custom title card bruh moments

See merge request STJr/SRB2!1501

Easing functions

See merge request STJr/SRB2!1467

Take slopes into account in FOF wall cutoff in HWR_ProcessSeg

Closes #192

See merge request STJr/SRB2!1361

NPO2 slope span optimization

See merge request STJr/SRB2!1216

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 STJr/SRB2!1504

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

See merge request STJr/SRB2!1413

tRNS chunk fix

See merge request STJr/SRB2!1393

Optimize Picture_GetPatchPixel

See merge request STJr/SRB2!1342

Remove music slot compatibility

See merge request STJr/SRB2!1321

Scale minimum dashmode thok speed on actionspd, not normalspeed

See merge request STJr/SRB2!1311

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

Closes #517

See merge request STJr/SRB2!1358

Make steam apply sprung flag

See merge request STJr/SRB2!1365

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

See merge request STJr/SRB2!1447

No fire shield palflash (resolves #512)

Closes #512

See merge request STJr/SRB2!1473

Change Raspberry's chat colormap to V_ROSYMAP

See merge request STJr/SRB2!1441

Add more actions for slope copying

See merge request STJr/SRB2!1406

Add linedef specials for multitagging in binary maps

See merge request STJr/SRB2!1485

The year is 2021

See merge request STJr/SRB2!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.