We want to know if there are debugging features compiled in, this may
affect performance. The message is printed before the sanity checks.

(This commit message is a copy of David Sterba's commit message when
he introduced btrfs_print_info()).

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>