- add an option for the output device in the hope that this can
be made non-blocking at some stage.
- define an alias for the disk device, required by dev/ofw/ofw_disk.c
- shift iobus to 0x9000000 so as not to clash with the OpenFirmware
entry point of 0x8000400 when address decoding.
- down-tone comments about the disk dev config :-)