make sure we can properly read UDP packets of any size

according to wikipedia:
```
The practical limit for the data length which is imposed by the
underlying IPv4 protocol is 65,507 bytes (65,535 − 8 byte UDP header −
20 byte IP header). In IPv6 Jumbograms it is possible to have UDP
packets of size greater than 65,535 bytes.
```
http://en.wikipedia.org/wiki/User_Datagram_Protocol

surely we have 65kB to spare..
provide feature to peek at bad lines flowing in
godoc