Free filerecs before exiting. This doesn't really make a difference in
memory usage but helps us test the free functions on a more regular
basis.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Start with first node in free_compare_tree

Otherwise we could leak some filerec tokens. While we're there assert that
we emptied the tree.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Merge branch 'filerec_free_fix'
Add SHA256 implementation from polarssl.git commit
82788fb63b7abc420e7d400f9d2948fd28add422

The following files are copied into duperemove.git,
without modification:

library/sha256.c -> sha256.c
include/polarssl/sha256.h -> sha256.h
include/polarssl/config.h -> sha256-config.h

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Add csum-sha256, using the polarssl implementation I imported in the
previous patch.

csum-gcrypt is disabled by default.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Remove gcrypt sha256 implementation. This allows us to drop the
dependency on libgcrypt.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Use murmur3 for default hash.

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