* libhgw/hgw_msg.c: Clean up hgw_msg_check_incoming()
* libhgw/: Implement internal incoming message queue. Some messages in the
    queue eliminate others, like state change notification. Would allow to peek
    into the queue in search of messages and user (app developer) would get
    most recent information by message elimination. Would also allow to
    implement function which checks current state more feasibly.


API:
  * Consider whether to allow termination notifying in hgw_notify_startup().
