Various compiling fixes

See merge request KartKrew/Kart-Public!212

Avoid underflows on connection screen timer (fixes hosting servers)

See merge request KartKrew/Kart-Public!211

Turns out compiling with the internal version of curl was broken on CMake the entire time 

Kill offroad line riding

See merge request KartKrew/Kart-Public!199

Fix timedemo in OpenGL mode

See merge request KartKrew/Kart-Public!209

Remove ESLOPE POLYOBJECTS POLYOBJECTS_PLANES #ifdefs (backport srb2 2.2)

See merge request KartKrew/Kart-Public!204

Fix replay recording memory leak

See merge request KartKrew/Kart-Public!208

Correct misplaced MT_ARIDTOAD listing

See merge request KartKrew/Kart-Public!206

Connection screen improvements

See merge request KartKrew/Kart-Public!187

2.2's random client port

See merge request KartKrew/Kart-Public!201

Instantaneous lookback camera (v2 backport)

See merge request KartKrew/Kart-Public!203

GME cleanup and fixes

See merge request KartKrew/Kart-Public!202

If we initialize to I_GetTime() - NEWTICRATE*3 it never underflows and everything is good

Just some stuff backported from SRB2 2.2, well mostly

get_zlib_error function to reduce code duplication

Return false if it fails to load the VGZ lump

Reduce redundant calls to gme_set_equalizer

Fix sometimes loading a VGZ crashing the game

If you ever need to, you can change the client port number.

(cherry picked from commit 843d9b9f)

Using strcpy is stupid because we don't know how long the argument would be.
There's no need for a buffer anyway.

(cherry picked from commit 4e321012)

(cherry picked from commit f584b61c)

This fixes '-connect'. NEWTICRATE*5 is subtracted from asksent after
CL_LOADFILES. If this happens too early, an underflow will occur.

Fix NOCURL compiling

See merge request KartKrew/Kart-Public!197

Let servers send httpsource without curl

See merge request KartKrew/Kart-Public!196

Lua Input/Output library

See merge request KartKrew/Kart-Public!200