to mixing them in with the ra* disks, modelled loosely on how MSCP
rx* floppies are handled
- racd* defaults to the same single iso9660 partition as cd*
- Cleanup config option handling slightly so any combination of ra*,
rx* (and now raccd*) can be defined without build errors.
- Avoid ugly printf when disks have all zero disklabel magic number
351c7b5d8f