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.