Add a draft of a script running testcases in SimulAVR.

This script also asks SimulAVR to generate pin traces of the X
and Y axis and even processes this data into a data file with
time, position and current speed of each axis.

Missing:

- Acceleration calculation.

- LOTS of polish.
run-in-simulavr.sh: also rewrite VCD file to add speed values.

This is quite handy, as you can see accurate speed ramps in
GTKWave now.
run-in-simulator.sh: use stdin/stdout for the data file, too.
run-in-simulator.sh: run (only) selected files.
run-in-simulator.sh: express velocities in mm/min, too.

Uh, this bloats the resulting VCD file by 50% ... ;-)