Hey, Emacs, we're -*-Text-*- mode!

- Allow verifying of cartridges even if the tape drive does not support
  formatting, i.e. Ditto 2GB and Ditto Max.

- Make a backup-copy of the header segments. This will not help too
  much when the cartridge really has been re-formatted, but might help
  in case of accidents, and in "--verify-only" mode.
