Log message:
Add RMD160 digests.

Log message:
Import `same' from pkgsrc-wip.  Packaged by Roland Illig.

The `same' utility looks for identical files and links them together
using either hard links or symbolic links, saving disk space.

Changes to the original version:
* the file ownership and permissions are checked.  (The original
  version checked only the file size)
* the messages in the "dry-run" mode were suggesting that anything on
  the disk would be modified.  They have been made clear.