Bug 6896: encode/decode a DNS query according to RFC 1035 zone file format as expected by Net::DNS API (what a terrible idea!), turn warning into info() for unmatching DNS responses

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/trunk@1438670 13f79535-47bb-0310-9956-ffa450edef68