(force/torque sensor needs new API)
in a nutshell, users of shared memory physics API should not
directly poke into shared memory, not fill 'SharedMemorCommand'
nor read SharedMemoryStatus directly. The C-API declares 'handles' for those,
to avoid it from happening.
only allow server to create and initialize shared memory,
client will report failure
intercept signals to cleanup shared memory in standalone app, thanks to
Roland Philippsen.
