
have run-time configurable debug messages.

Current situation
cpu:
- PCLOG
- some #ifdefs to remove (PROFILE, MONITOR)
- interrupts
- VBL

cpubis
- exceptions (some reported, some not)
- traps

mfp: 
- possible to trace r/w on mfp registers
- trace interrupts ?
- trace timers?

mfp: TODO, timer B?


command would be:
trace bios all
trace bios -12 -13   # all except 12.
trace xbios


