Update code versions to 2.1.21

See merge request STJr/SRB2!338

Block previous versions' config defaults with EXECVERSION consvar

See merge request STJr/SRB2!371

* Change alwaysfreelook2 to be consistent with alwaysfreelook (the only one that wasn't the same)

Controller defaults: Set Ring Toss to right trigger instead of left trigger

See merge request STJr/SRB2!370

Change 2p controller defaults

See merge request STJr/SRB2!369

Add OS and 32/64-bitness to VERSION console command

See merge request STJr/SRB2!368

Fix 64-bit build-using admins not being able to kick players besides themselves, by not checking sendingsavegame[] code at all if not the server

it turns out playernode[pn] is typically 255 in the above situation, so sendingsavegame[playernode[pn]] goes out of bounds ...but goodness knows why 32-bit builds didn't suffer the same bug, seems to have been pure luck

It turns out the game was sending the full size of the motd buffer (254) rather than just the size of the string made, therefore sending a load of garbage and making the game apparently execute unknown or illegal net commands

Fix the game being basically broken due to multi-admin, by porting over some missing changes from Kart

Use Joystick 1 and Joystick 2 by default if plugged in

See merge request STJr/SRB2!364

Joystick juggling

See merge request STJr/SRB2!355

Slightly re-organize DLLs and document the required list for bundling

See merge request STJr/SRB2!365

Make uninstaller a self-extractable

See merge request STJr/SRB2!367

Tiny Makefile Fix

See merge request STJr/SRB2!289

Add old-install-list.txt to explicitly define which old install files need to be moved

See merge request STJr/SRB2!366

Replaces MoveOldExeDlls routine in installer staging

Reason for this is because the SDL2 binaries live in libs/ for ease of copying. The DLLs ought to be in one location.

https://github.com/jrfonseca/drmingw/releases/tag/0.9.0

Update OSX icon

See merge request STJr/SRB2!363