Implement OSX and Debian installer building for Travis

See merge request KartKrew/Kart-Public!8

Minimum speed to get drift sparks

See merge request KartKrew/Kart-Public!20

Add Windows installer building and 64-bit builds to AppVeyor

See merge request KartKrew/Kart-Public!7

Gamepad Improvements

See merge request KartKrew/Kart-Public!5

# Conflicts:
#	CMakeLists.txt
#	appveyor.yml
#	src/command.c
#	src/command.h
#	src/d_clisrv.c
#	src/d_netcmd.c
#	src/dehacked.c
#	src/doomdef.h
#	src/hu_stuff.c
#	src/m_misc.c

Add a global for mobjscale

See merge request !10

Merge SRB2 master & next (round 1)

See merge request KartKrew/Kart-Public!16

Cast animtimer to int before negating

See merge request KartKrew/Kart-Public!17

Compile flag for DEVELOP

See merge request KartKrew/Kart-Public!18

Stops a Visual Studio compile error.

Remove facefreed/iconfreed

See merge request KartKrew/Kart-Public!15

Load sounds.kart after patch.kart

See merge request KartKrew/Kart-Public!13

Had issues with skin values not changing from the menu, this seemed to fix it

Caused an issue where having more than 16 characters loaded would crash the game when compiled with MSVC.

Fix unsigned abs errors

See merge request KartKrew/Kart-Public!14

(it was never in the original travis script)

* Use sdl2_mixer from mazmazz/srb2 due to removed options from homebrew-core
* Use `brew install --build-bottle` to build compatible libraries for old Macs

Don't increment mainwads for sounds or music.kart

See merge request KartKrew/Kart-Public!12

Resolve buffer overflow crash when configuring System Menu and GIF controls

See merge request STJr/SRB2!445