Send blank NTP packets

Mostly scaffolding so far.

This sends 48-byte data packets based on the appendix to [RFC958](http://tools.ietf.org/html/rfc958).  The first four 32-bit chunks are random stuff, the last four 64-bit chunks are timestamp values.  A timestamp has a 32-bit unsigned integer part and a 32-bit unsigned fractional part.

Hopefully you could send a blank packet to an ntp server and get a meaningful response?