libsmack 1.1: support loading of netlabel configuration

[rafal-krypa]

There seems to be a need for loading Smack netlabel configuration at boot time. In Tizen, there is a non-upstream modification to Smack support in systemd, adding this feature (https://review.tizen.org/gerrit/gitweb?p=platform/upstream/systemd.git;a=commit;h=refs/changes/67/13567/1)
If we try to send patches for upstream systemd to perform Smack tasks with libsmack instead of reimplementing it, such changes couldn't be ported to Tizen. That's because libsmack cannot load netlabel configuration.

Therefore I suggest adding such functionality to smack_load_policy() function.