o Better keep track of current global absolute position by re-using the parser in multiple
  invocations of gcode_machine_control_from_stream(). It might be called multiple times from
  different TCP connections. Creating a new parser each time meant a disconnect between the
  absolute position it thinks (0, 0, 0) and the machine coordinate the machine control kept
  track of.
o Bubble up error messages from motor-interface and parser internals to the error stream. That
  way, parse errors are reported as well to the TCP connection.
o be a bit more conservative with the default max feedrate, as we
  don't do acceleration yet.