New Deadwood snapshot: dwx_check_answer_section

I have created a second Deadwood snapshot today; as I get going working on recursion, I will at times make multiple Deadwood snapshots in a single day.

In this snapshot, I have added a function called dwx_check_answer_section, which goes through the answer section of a remote DNS reply and marks answers which are not either a direct answer to our question or part of a CNAME chain leading up to an answer to our question as RRX_IGNORE. In other words, it tells Deadwood to ignore answers which don't answer our question.

Next: Revise dwx_check_answer_section to not allow CNAME chains after a direct answer to our question is found or an answer at the end of a CNAME chain is found. Then: Add code which links up NS replies in the NS section with A and AAAA glue replies in the AR section.