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.)
Now check all reads for exceeding end of disc and info messages can be
logged. We were also returning 0 on error reads. Regularize by using a
couple of macros.
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.
