XDisplayControlPlugin provides primitives for controlling the connection to
an X display server for Squeak. Currently, this is useful for the Unix VM,
but in principle can be used for any platform that can provide an X server,
such as Win32, Mac OS, or OpenVMS. A running Squeak image may call these
primitives to become headless, to open a display on an X server from a headless
Squeak, or to connect itself to another X server.

Dave