Last-minute fixes

See merge request !1483

This reverts commit c51c4787.

Give TOL_ERZ3 an appropriate identifier (closes #516)

Closes #516

See merge request !1471

Let Lua cvars use preset values in addition to MIN and MAX

See merge request !1480

Unset zstring if a preset value is used

Closes #487

See merge request !1479

This is only applicable for bounded cvars (MIN, MAX),
since otherwise there's no way to allocate a zstring.

Cvars could now have a range (MIN, MAX) plus some preset
values, but Lua could not take advantage of this due to
table order not being guaranteed.

Fix a dedicated crash in Special Stage intermissions (2.2.9 RC1)

See merge request !1475

Spritedef add hotfix

See merge request !1476

Possible netgame quit crash hotfix

Closes #487

See merge request !1477

Set "allocated" flag to off if setting a string from PossibleValue afterwards, or if not setting a new value at all.

Fix uninitialized reads in PreparePolygon

See merge request !1392

Render midtextures on two-sided lines with a z-buffer offset

See merge request !1376

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

Closes #295

See merge request STJr/SRB2!1462

Fix incorrect values caused by outdated use of timing functions in perfstats 3

See merge request STJr/SRB2!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 !1458

Fix HWR_DrawSprite sigsegv

See merge request !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