identical to the previous incarnation.
- Update using m68k asm.h macros
- Move initialization towards the front of the file
- Rename mac68k_buserr_addr to m68k_fault_addr
- Reorganize trap 15 handler, similar in structure to -- though not as
complete as -- the hp300 version
- Reorganize doboot() for easier integration of external cache, and
make room for the latter (#ifdef __notyet__)
- General garbage collection of unused code/data