Put MAGIC macros into the DNS_ namespace.
Take name cleanup code from msgreset() and put it into msgresetnames().
In dns_message_create(), the intent is now specified before the returned
message pointer.
dns_message_reset() now allows an intent to be specified.
msg->header_ok is set if parsing the header succeeded, and msg->question_ok
is set if parsing the question section succeeded.
Added dns_message_reply().