This is incompatible with the previous implementation

 - sequence number is 32 bits
 - frames are 1,2,3 not 0,1,2 (so to be *more* incompatible)
 - no fake latency values are printed if frames are lost
 - the message is one line instead of two, and cleaner too
 - the sender reminds it's sending every 10s.

The receiver's messages now include the sequence number, so we can
match different receivers on a network.  Also, The sender's message
report both TAI and sequence, so we can related frames to the time of
day.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>