EDNS if the remote server doesn't understand EDNS.
In certain error cases during the construction of a query the resolver tried
to free data twice.
Set AD and CD when making EDNS queries.
If resquery_send() fails after a TCP connection is established, fail the fctx
the same way we do for the UDP case.
Revisions in preparation for DNSSEC validation.
If we get a non-EDNS-related FORMERR from a server that is not a forwarder,
assume that all servers for the zone will return FORMERR.
Cope with YXDOMAIN.