Update status items on blob events.

Update status items on blob events.

If the image or the lyrics blob for the current audio file changes,
e.g. because the user executed the mvimg command, para_gui still
reports the old value because blob events don't trigger a status item
update.

This patch teaches aft_event_handler() to honor such events. We keep
it simple and update the items on every add/remove/rename event.