Test script: (re)store events

This triggers unpacking of traces, and on the Pi, CPU usage is between 50
- 80 %, mostly at over 60 %.  And yes, the hardware froze.  It almost
certainly has something to do with readout frequency, as it ran for over
three days without a hitch when it *didn't* unpack traces.
Rewrote unpack_raw_trace.  Much faster.

Love it!  It is over forty times faster, measured on my Mac.  On the Pi,
it is even 50 - 60 times faster!!  Woot!

With this modification, test_hv hovers at 14 % CPU usage.