In order to sync ctree.c we're going to have to have definitions for the
tree-mod-log stuff. However we don't need any of the code, we don't do
live backref lookups in btrfs-progs, so simply sync the header file and
stub all the helpers out.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
