NAME
       XorRectRegion -- Perform 2d XOR operation of rectangle
                       with region, leaving result in region

   SYNOPSIS
       status = XorRectRegion(region,rectangle)
         d0                     a0      a1

	 BOOL XorRectRegion( struct  Region *, struct  Rectangle * );

   FUNCTION
	Add portions of rectangle to region if they are not in
	the region.
	Remove portions of rectangle from region if they are
	in the region.

   INPUTS
       region - pointer to Region structure
       rectangle - pointer to Rectangle structure

   RESULTS
	status - return TRUE if successful operation
		 return FALSE if ran out of memory

   BUGS

   SEE ALSO
	 OrRegionRegion()  AndRegionRegion()  sc:include/graphics/regions.h