Jurl: MS-DOS Edition

Another port of Jurl, this time to DOS.

It *works*, in the sense that the game features are all present. However:

• I've only managed to test it in DosBox
• Not in the slightest performant, i'm optimising but still definitely not there yet.
• SoundBlaster support sort of works, it's patched together from some very perfunctory research.
• Performance still isn't great, especially in EGA