DNS corrections

Give back NXDOMAIN when a service isn't found.
Also set the AA bit on replies (skydns is authoritative for this stuff)
and announce to be capable of doing recursion (RA bit).
Include SOA record in NXDOMAIN

The rules state NXDOMAIN requires a SOA record in the reply.
Make that happen.
Remove qtype == ANY here, already handled

This is handled in the 'if' above it. It can be removed here.
Send NODATA for unsupported record types
Make sure the correct bits are set when DNS forwarding
Merge pull request #61 from miekg/dns

Fix DNS replies