Mostly wrong test counts.

In the pkt tests, the comparison test is failing, but don't know
why. It's somehow related to the OPT RR, because when I remove its
addition, it doesn't fail anymore. However, I don't know what's
the problem yet.

- knot_edns_init_from_params() modified to add also empty NSID
  OPTION.
- knot_pkt_add_opt() documented and modified usage not to insert
  emtpy NSID to reply.
- OPTION printing in utils was not implemented.

change.

- remnant of libknot separation I guess.

Signed-off-by: Jan Kadlec <jan.kadlec@nic.cz>

Conflicts:
	tests/requestor.c

Was adding the NSID even if it was empty.

Note: maybe it would be better not to support adding empty options.
TODO: add some checks to unittest, related to this.

- Unittest for setters.
- Enabled EDNS unittests.
- Fixed unittest messages.
- Fixed wrong parameter check in edns_has_option().
- Fixed all EDNS unittests.

All tests pass. Hopefully it means something...

Unittest for requestor.c needs fixing (wrong argument).

Not even compiled yet.

Conflicts:
	src/knot/server/udp-handler.c

protocol-agnostic response, copied socket for deferred cleanup
The copy is needed so the TCP worker can close the socket and
the connection is held until the UPDATE request is cleared.

The MSG_WAITALL doesn't work as expected everywhere and
can return partial answer (for example with signal interrupt).
Also implemented timeouts for TCP receive.

Previously, response was paired to query according to the Message ID
and QUESTION. This however doesn't work for zone transfers, as some
servers omit the question section for multi-packet answers
completely.