This is the verbatim copy of what I wrote as example code for an
article about time stamping. It's called "mini time protocol".  Some
of the code, in turn, comes from my previous experiments with White
Rabbit.

I'd better have the programs here as I use them often. As time permits
I'll add some more features and documentation in the ppsi manual.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>