This lets the host manually remove a body if they want,
without polluting the chat with redundant messages.

Disconnected players do not become IT at round start.

If all non-ITs are disconnected, the round ends.

If all ITs are disconnected, one of the non-ITs
becomes IT, or the round ends if in Hide & Seek.

# Conflicts:
#	src/g_game.c
#	src/p_setup.c

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.

OpenGL drop shadows

See merge request STJr/SRB2!703

Put cv_exitmove in the server options menu

See merge request STJr/SRB2!704

Mapthing flag EXTRA DeHackEd constant

See merge request STJr/SRB2!705

Add FF_INTANGABLEFLATS as an alternative spelling for FF_INTANGIBLEFLATS

See merge request STJr/SRB2!702

Software dropshadows

See merge request STJr/SRB2!660

Add R_IsPointInSubsector to lua baselib

See merge request STJr/SRB2!700

Fuck NONET

See merge request STJr/SRB2!699

Fix FF_INTANGABLEFLATS typo

See merge request STJr/SRB2!701

fuck it, hopefully it works

Add missing name to the credits

See merge request STJr/SRB2!696

Larger chat

See merge request !691

Try to set a 21 character name and SIGABRT

See merge request STJr/SRB2!689

-bindaddr for mserv

See merge request STJr/SRB2!688