Convert old frame flags in Metal recordings to their 2.2.10 equivalents

Closes #775

See merge request !1742

This reverts commit b2d693a5.

Fix blendmode V_ flags not working at full opacity in Software

See merge request !1717

Remove MT_NULL hacks

Closes #721

See merge request !1729

Increase Eggman's hitboxes

See merge request !1706

Improve bots (resolves #710)

Closes #710

See merge request !1679

Fix portals

See merge request !1724

Fix #732

Closes #732

See merge request STJr/SRB2!1739

Allow people to update their Master Server listing on command.

See merge request STJr/SRB2!1518

Disable SDL error message on dedicated servers

See merge request !1735

Fix crosshairs not displaying

See merge request STJr/SRB2!1716

Fix lock-on crash (Resolves #746)

Closes #746

See merge request !1704

Fix software splats breaking and crashing in skyboxes

See merge request STJr/SRB2!1711

Fix software splats not being clipped by ceiling walls

See merge request !1712

Hack that fixes software drop shadow crashes (Fixes #159)

Closes #159

See merge request !1700

Add missing optimization to software npo2 sloped floor sprites

See merge request !1713

Fix issues with chat messages

Closes #583

See merge request !1698

Do not attempt to disconnect when a packet checksum is invalid

See merge request !1699

UDMF: Fix offset calculation for segs that represent linedef backsides

See merge request STJr/SRB2!1701

Only load map lumps that are WADs or have no extension

See merge request !1715

So they don't mess with shell scripts that expect SRB2 to exit when it crashes (like most other programs)

Checks if P_TryMove would succeed without actually moving.

MT_NULL spawning, not cool bro.

Don't modify drawangle when taking damage in strafe mode

See merge request STJr/SRB2!1689

Fix Nightopians

See merge request !1703

Fix A_OldRingExplode not scaling or flipping

See merge request !1709

- Resetting portalcullsector fixes the major visual glitches

- Using 32 bits for nummasks and i fixes crashes when rendering lots of portals