ch12 contains the following example programs:

xscrollbox:	a simple version of xbitmap that tests ScrollBox

ScrollBox.c:	source file for a minimal composite widget that manages 
		two scrollbars and a main window

ScrollBox.h:	public include file for ScrollBox

ScrollBoxP.h:	private include file for ScrollBox


BUGS: 		for some unknown reason, the borders in the children of
		xscrollbox are modified

		the handling of the Motif scrollbars is not quite correct
		or complete (for real examples of using it, see Volume 6 and
		the associated examples)
