NAME:
	negative
 PURPOSE: (one line)
	Invert the current display lookup table.
 DESCRIPTION:
	The current lookup table is fetched, rotated end-for-end, and put
	re-loaded.
 CATEGORY:
       Image display
 CALLING SEQUENCE:
	negative
 INPUTS:
	None.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD PARAMETERS:
 OUTPUTS:
	Modifies current lookup table.
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
	Written by Marc W. Buie, Lowell Observatory, 1991 Oct 29.