Skin unlockables / skin emblems are now checked at runtime to see if there's any matches.

Locked skins now are a specific unlockable type, instead of being tied to the skin's properties.

This has plagued custom gamedata since 2.2 launch. It's extremely obnoxious having to set aside random numbers as dummy unlockables just to ensure that Amy Fang & Metal are unlocked from the start in a custom map pack.

Other changes made to accommodate this:
 - R_GetSkinAvailabilities is now created from the list of unlockables set to skin type. (1st skin unlockable defined is (1), 2nd skin unlockable defined is (1 << 1), etc...)
- The "Added skin x" print shows up when loading addons but not at all for the base game, because the previous behavior of hiding based on if the skin was locked would now require iterating unlockables, which felt wrong to do during that stage of the loading process
 - I noticed in my test wad that Sonic&Tails would give you Sonic&Sonic out if Tails was locked. I fixed that by making both skins required to show the character select option.

Mods that reserved empty dummy unlockables for Amy Fang and Metal won't have to do anything. Mods that wanted to re-lock them behind different requirements will have to update, but in the future they will not have to be in specific slots. Additionally, now Sonic Tails and Knuckles can also be locked for mods.

Remove bad pointer arithmetic in polygon comparators (fixes #295)

Closes #295

See merge request !1462

Fix incorrect values caused by outdated use of timing functions in perfstats 3

See merge request !1460

Cache teamflags/icons before drawing if they don't exist yet (closes #511)

Closes #511

See merge request !1459

Fix blend tables generation

See merge request STJr/SRB2!1458

Fix HWR_DrawSprite sigsegv

See merge request STJr/SRB2!1454

Blending changes

See merge request STJr/SRB2!1446

Fix CTF flag patch garbage (resolves #506)

Closes #506

See merge request !1453

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

Closes #453

See merge request !1451

Fix a OpenGL backend DeleteTexture crash (Fixes #499)

Closes #499

See merge request !1448

BRUH MOMENT

Fix jet fume crash when dashmode is above DASHMODE_MAX

See merge request !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 !1449

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

Closes #389

See merge request !1440

Smoother freelook in Software

See merge request !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 !1432

Prevent a single client from blocking Lua file transfers

See merge request !1435

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

See merge request !1445