support_format_dns_packet: Fix CNAME and multiple RR handling

Before this change, the loop iterating over RRs in the answer
section stopped at the first CNAME record, never printing them.
The CNAME and PTR record contents was extracted from the wrong
buffer (whole packet instead RDATA).  This desynced the parsing
after the first CNAME or PTR record.

Also fix the AAAA record parsing by checking their sizes.