Initial version bringing in code from miekg/dns so we can modify it to handle responses
Remove Net choice in response-listener code
Don't need 'started' logic
Inline read timeout
Don't bother testing PacketConn - crash if problem
Inline serveUDP()
inline buffer size
Simplified serve()
Rename ResponseCallback to ResponseReceived
Rename to ResponseListener
Don't handle each response on a separate goroutine
Inline handle() function
Simplified ResponseListener
Print warning on DNS message format error