This is accomplished by simply preserving
the player's body after disconnecting.

Bodies will despawn after the number of minutes
specified by the "rejointimeout" console variable (float).
A value of 0 disables the feature completely.

Clients rejoining are identified by their IP address,
and may rejoin even if the server is full or joins are disabled,
for as long as their body remains.

From a technical standpoint, when the user disconnects,
the player they were controlling does not leave,
the underlying player_t just keeps working normally,
except it does not receive any input anymore.
When the user reconnects, they are simply "relinked"
to their player_t.

Those "soulless" players can be identified through
their "quittime" field, which is the number of tics
elapsed since the user disconnected, or zero
if still connected. "quittime" is exposed to Lua.

Get 2.2(.0) release ready

Closes #461

See merge request STJr/SRB2Internal!615

Lengthen credits for msuic parity

See merge request STJr/SRB2Internal!620

Update SRB2 Community Contributors list for Revan's Nimbus Ruins skybox.

See merge request STJr/SRB2Internal!621

Add "Press ENTER to skip..." text to the intro's first scene

See merge request STJr/SRB2Internal!619

Date stuff

See merge request STJr/SRB2Internal!618

Signpost fixes

See merge request STJr/SRB2Internal!602

Add "Press ENTER to skip..." text to the intro's first scene, for new players who might otherwise sit through a load of (polished) crap. :P

Small analog mode fixes

See merge request STJr/SRB2Internal!604

Fix F12 issues

Closes #356 and #377

See merge request STJr/SRB2Internal!616

OpenGL cast to float, not store in double

See merge request STJr/SRB2Internal!617

Remove unnecessary function parameters from title card code

See merge request STJr/SRB2Internal!603