PCL5E, PCL5c, PCLXL, and HPGL/2 with RTL. All of the PCL products
use the Ghostscript Graphic Library for graphics, imaging and driver
support.
TODO:
: not yet tested on anything but 1.6ZD/i386
: find a way to let GHOSTPCL_USE_X11 default depend on the presence
of /usr/X11R6