(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

Push bouncing players backwards if they get stuck in a wall

See merge request KartKrew/Kart-Public!3

Fix per-map palette not being reset properly when it should.

See merge request KartKrew/Kart-Public!9

Add waypoint lap field via Parameter field

See merge request KartKrew/Kart-Public!4

How did this even get reverted...

This reverts commit 1bb6ff27.