This GRASS driver replaces the the old "SUN" driver which relied on
the SunCORE graphics library.  Besides being used for years, this
driver had the following drawbacks:
  1 Relied on the SunCORE library which is not available on all SUNs
  2 Had to work to get around the fancy SunCORE capabilities to
    address individual pixles.
  3 The SUN graphics window could not be resized, uncovered, or iconified.

Several people contributed to this driver:
  Bruce Schwartz of SUN wrote the original driver for GRASS 2.0 and then
     added the Panel routine to the GRASS 3.0 version.
  Jim Westervelt of CERL converted the 2.0 driver to the first 3.0 version.
     He also added resizing and a graphic icon.
  Dave Johnson of DBA did some major debugging.

Tasks left:
  1 Resizing the canvas seemed to render the pw_rop functions in 
    Raster.c and Panel.c impotent.   After a resize, the pw_rop became
    a no-op.    After much experimentation, I decided to destroy the
    old canvas on a resize followed by the creation of a new in its
    place.  This ensures that the canvas is never resized thereby 
    ensuring the pw_rop function always works.
  2 The de-iconification generates a resize event which destroys
    the stored picture.  
  3 Raster overlays (which display only pixles with non-zero categories)
    are currently generated with move and line-draw functions.  To speed
    this up attempts to use pw_stencil (Raster.stencil) or pw_read
    (Raster.rw) were made.  This are as yet unsuccessful.
