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.)
or ATAPI or whatever.
cdda_interface: Use mmc_have_inteface() we don't have anything for
this except in GNU/Linux. May reduce the unnecessary data_bigendianp()
calls which cause lots of disc reading.
Turn #defines for MMC Profiles into enumeration.
Add enumeration for "core" interface types
#include <cdio/scsi_mmc.h> -> #include <cdio/mmc.h>
