I have refactored a lot of the code, including cleaning up and moving the basic to lower memory. ehBasic may be free and powerful, but it is also quite a mess in places.

I can now load 2 instances of basic, each using a separate serial port. Both are running in fully separated 64KiB memory windows, except for the HW ports. The main reason to run 2 basics is to test thread communication, which I'll start on next.