Building under Ubuntu 22.04

[jduerstock]

I'm not sure what distribution you use, but I had to do a couple of things to get this to build under Ubuntu 22.04:

1. replace '#include "SDL.h"' with 'include <SDL2/SDL.h>"
2. sudo apt install libsdl2-dev:i386 lib32gcc-11-dev

I also had to change my /etc/apt/sources.list so it would find the i386 packages, but I'm not 100% sure I did this cleanly.

[icculus]

I happened to have SDL laying around for some reason. :) But this is probably something that needs to be simplified or documented better.