Should help with ISO 9660 reading. Add generic MMC READ_CD routine.
Warning - even more breakage in some situations. (But there's promise
of an overall brighter future.)
read.{c,h}: separate include for the reading routines.
disc.{c,h}: more moved here from corresponding cdio.
device.c: a place for device/driver related routines.
interface.c: break up line to make debugging easier.