Also fixed possible issue with incorrectly reading the demo pointer due to the wrong type being passed to sizeof in G_ConsGhostTic

Model fallback

See merge request STJr/SRB2!1167

Bustable Wall and Floor flags.

See merge request STJr/SRB2!1163

Performance stats

See merge request STJr/SRB2!1186

R_FindPlane optimization

See merge request STJr/SRB2!1199

Apply step up/down to opposite plane too

See merge request STJr/SRB2!1192

Lua polyobjects

Closes #19

See merge request STJr/SRB2!1140

Make record attack's quick retry more consistent.

Closes #80

See merge request STJr/SRB2!1193

Fix OpenGL GIF recording crashing with gif_localcolortable disabled

See merge request STJr/SRB2!1196

Fix gzip failing to compress SRB2's objdump on non-Windows.

See merge request STJr/SRB2!1191

Software 3D floor rendering optimization (second attempt)

See merge request STJr/SRB2!1184

Allow JumpSpin abilities to be used with non-ability shields

Closes #277

See merge request STJr/SRB2!1146

Save netvars

See merge request STJr/SRB2!1179

Give the addfile command variable argument support.

See merge request STJr/SRB2!1176

Shader code cleanup

See merge request STJr/SRB2!1103

I am going to die :D (closes #337)

Closes #337

See merge request STJr/SRB2!1183

Fix clients being able to skip credits AGAIN (closes #339)

Closes #339

See merge request STJr/SRB2!1182

A special stage is a special stage, even outside of coop.

Closes #211

See merge request STJr/SRB2!1180

Don't count demo playback as visiting a level.

Closes #327 and #340

See merge request STJr/SRB2!1177

Add `-splitscreen` commandline parameter

See merge request STJr/SRB2!1175

Add P_CeilingzAtPos function

See merge request STJr/SRB2!1164

showjoinaddress
maxplayers
joindelay
rejointimeout
resynchattempts
blamecfail
maxsend
noticedownload
downloadspeed
jointimeout
maxping
pingtimeout
servername

dumpconsistency
allowjoin
joinnextround
restrictskinchange
allowteamchange
startinglives
respawndelay
competitionboxes
allowseenames
matchboxes
specialrings
powerstones
countdowntime
touchtag
hidetime
autobalance
teamscramble
scrambleonchange
friendlyfire
overtime
pointlimit
timelimit
basenumlaps
allowexitlevel
inttime
coopstarposts
cooplives
advancemap
playersforexit
exitmove
pausepermission
respawnitemtime
respawnitem
flagtime

tv_recycler
tv_teleporter
tv_superring
tv_supersneaker
tv_invincibility
tv_jumpshield
tv_watershield
tv_ringshield
tv_forceshield
tv_bombshield
tv_1up
tv_eggmanbox