Initial port of Jedi Academy back to gcc/unix

Here are the initial parts to make Jedi Academy compile and run. Save games are not yet handled properly on amd64 due to some horrible pointer casts in the original code.

Loading levels on amd64 seems to skip the cutscenes and not properly set everything up.  I don't see this problem with Jedi Outcast however.

The multiplayer code is currently not ported, only single player.

Tested on OpenBSD (i386 and amd64) and linux (i386), I don't have a windows compile environment here but I've tried not to break windows while doing this.

Data from the demo seems to work somewhat differently and gets stuck in the menus and acts odd when loading maps, the full game data from steam seems to work fine however.