An mc6809 emulator written in C++

NB: version 0.91 is historic (written in 1993!) and has some serious known bugs in the handling of some instructions and addressing modes. Many thanks are due to B. Armstrong and Soren Roug for finding and resolving those.

The master branch on the primary Github repository (https://github.com/raybellis/usim/) now contains fixes for those issues.

• Interrupt handling (inc. SYNC and CWAI instructions)
• many other things I probably didn't think of yet