JK2 Support

Sorry for the additional noise, I got JK2 working right after I filed that last pull request. JK2 now seems to work. The opening cutscene loads, and the first map seems to be working correctly and playable.

Note: This was only tested on Gentoo Linux x86_64. The x86_64 build of OpenJK was used.

It also appears that user saving is broken. I will investigate.