- hash_tree num_blocks and num_hashes members should be 64 bits wide

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
- print a message to the user when duperemove begins the process of
  finding duplicates. This makes it easier for users to know when
  checksumming has completed.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>