Log Message:
Add lang/cbmbasic, a Commodore BASIC interpreter

Imported from wip.

"Commodore BASIC" (cbmbasic) is a 100% compatible version of Commodore's
version of Microsoft BASIC 6502 as found on the Commodore 64. You can use it
in interactive mode or pass a BASIC file as a command line parameter.

cbmbasic does not emulate 6502 code; all code is completely native. On a
1 GHz CPU you get about 1000x speed compared to a 1 MHz 6502.