Request 30322:  Additions to Xm structure

The following functions have been added to the Xm structure:

Xm.Pixel.fromWord32  : word32 -> pixel
Xm.Pixel.toWord32    : pixel -> word32

Xm.Display.visual_type = 
  STATIC_GRAY | GRAY_SCALE | STATIC_COLOR | 
  PSEUDO_COLOR | TRUE_COLOR | DIRECT_COLOR

Xm.Display.defaultDepth  : display * screen -> int
Xm.Display.defaultVisual : 
  display * screen -> {vis_type: visual_type,
		       r_value:  word32,
		       g_value:	 word32,
		       b_value:  word32,
		       rgb_bits: int}

Xm.Widget.backing_store = NOT_USEFUL | WHEN_MAPPED | ALWAYS
Xm.Widget.setBacking   : 
  widget * backing_store * word32 * pixel -> unit
Xm.Widget.setSaveUnder : widget * bool -> unit












