Another patch from Garrett: remove bad block bitmap checking code. Everything

Another patch from Garrett: remove bad block bitmap checking code.  Everything
produced in the list ten years has some variant of internal error correction
(disks, cdrom, flash), so if it has user-visible bad blocks on it the
hardware has exhausted its remapping reserve and is dying, and you need to get
your data off pronto.  (The one exception I can think of is floppies, and I
don't care.)