Tape Host Info Globbing

Situation

  There's a bunch of picky host specific details that are currently
  included in each of the tape definitions.  We ought to be able to
  define these for each host (rather than for each tape drive) so that
  there's more info sharing.

Implementation

  Rewrite read_config or whatever its name was) to recognize a "host"
  definition, which would include things like:

	mt status ok		whether mt status reports the correct
				file position

	mt eom works		whether mt eom works correctly and 
				reliably

	backup path		path to the backup stuff on this sort
				of host, eg /usr/local/nbackup/bin,
				used for finding dd and pmt

	os type			some identifier for the OS of the
				remote system - eg, ultrix, sunos4

  Change the tape definitions to include a host type entry, and
  eliminate the other gunk.

  It might be nice to extend this, so that we can say that host
  allosaur is type sunos4-a, with its backup programs in
  /usr/local/backup/bin, and change things so that this overrides the
  defaults when all-backups goes to run things on allosaur.

Other Points

  There are several problems with the way that backup-* and do-backups
  work as things stand.

  These ought to use specific info about the remote tape host to find
  things like the path for the dd or mt commands, or to find the
  backup programs.

  In some cases, we want to use the type of the local and remote
  system to determine how best to run the archive program.  For
  example, using Ultrix dump to dump to an Ultrix remote tape, we
  don't want to include the o option so that things will work most
  efficiently.  Otherwise we do.