Previously it seems to have worked by accident (there was not enough
space for the end NULL byte).

This allows adding of new commands without any changes to command
parsing and generation code.

Now both sides of a connection are seen:
  input  -> output(s)
  output <- input

OS X install do not support long command line parameters.

Some very old and broken compilers complain about shadowing bcopy().

After sending command to videohub the response must read before
another commands is sent.

This prints the device configuration as videohubctrl parameters thus
allowing the configuration to be restored later.