Patching to make compatible with appengine/socket.

The interface conversion from socket.Conn to net.UDPConn fails, but
since you can use a generic Read(b) in place of ReadFromUDP(b) it makes
sense to git rid of the conversion to net.UDPConn.  This change allows
the use of the client library for UDP DNS lookup using the
appengine/socket package's Conn.

For the same reasons the interface conversions for TCP connections were
also removed.
Further patching for GAE compatibility.

Since net.ListenTCP, net.ListenUDP and net.TCPListener are not defined
in the GAE standard library these build flags will stop those files from
being imported.  A better solution would have been to break up this
monolithic package into smaller parts.
Still more patching for GAE compatibility.

After removing some of the server files from the GAE build we hit
another undefined: ResponseWriter.
Merge pull request #58 from gavaletz/master

Make DNS Client compatible with Google App Engine.