Fix cv_usejoystick being reset to None when cv_usejoystick was > NumJoys and changing to already-used joystick

Fix menu where cv_usejoystick.value > I_JoyNum and selecting an unused controller and the "used!" prompt pops up erroneously

* Menu improvements to tell the user that they can't set a controller if it's already active

* Don't save cv_usejoystick/2 because hotplugging changes can be made invalid by next run
* Properly set cv_usejoystick/2 for menu toggling
* Force-disable a player's joystick if setting another player's joystick to the same device
* Properly set cv_usejoystick/2 value of BOTH target player AND other players when hotplugging and unplugging

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)

(with log messages)

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