Changes to potato (old disksets removed)

[Richard Braakman <dark@xs4all.nl>]

- Removed 2.0.11.4, 2.1.8, and 2.1.99.0 disksets from disks-powerpc.
   (superseded by 2.2.1)

- potato/main/disks-sparc is now a directory, rather than a symlink to sid.
  sid's disks-sparc is removed entirely; the diskset in slink was newer.

- Removed 2.2.1 and 2.2.2 disksets from disks-i386 (superseded by 2.2.3)

Together this freed up 285 MB, yay!

Richard Braakman