- Don't compare the same files more than once
  - we track file comparisons on a per-filerec rbtree
  - this gave me an enormous performance benefit on a run of my build disk
    hash file (from 3 minutes to about 15 seconds).

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
- replace duplicate extent check list walk with a tree lookup
  - de_extents is only used in duperemove.c and can be removed once those
    sites are fixed up.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
- remove files_compared item from rbtree before freeing it.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Merge branch 'performance'
Fix build of filerec-test

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