todo:
* Probing/Conflict resolution
* uniqueness
+
* defend our entries on incoming goodbye
* Unicast responses/queries
* Legacy unicast
-* Known-Answer suppression server part
-* Truncation
-
done:
* really send goodbye packets
* refresh subscribed records only
* FLX_DNS_TYPE_ANY support
* Known-Answer suppression client part
-
+* Known-Answer suppression server part