- Added packet_parse_rest() to parse the rest of the packet from
  wireformat.
- Modified ns_parse_packet() to parse only the Question section.
- Modified ns_answer_normal() to parse rest of the packet.
- ns_answer_axfr() does not need any other parsing (we may ommit
  the OPT RR).
- Modified axfrin_transfer_needed() to parse rest of the packet.

refs #800 @1h