* Fix $op 'delete' on hook_locationapi().
* API CHANGE: Use location_save_locations() with an empty array instead of deleting rows from {location_instance}. This lets us have "real" deletion instead of relying on garbage collection.

Before:
<code>
db_query("DELETE FROM {location_instance} WHERE genid = '%s'", 'mykey:'. $obj->id);
</code>

After:
<code>
$locations = array();
location_save_locations($locations, array('genid' => 'mykey:'. $obj->id));
</code>

* Remove garbage collection routine and UI from settings page. References are checked automatically now.