Squashed commit of the following:
apps/graphics/twm4nx: Revamp the event system to support notification of external applications when the window is being closed.
apps/graphics/twm4nx: A little NxTerm progress
apps/graphics/twm4nx: Clean up some logic associated with use of multiple Icon Managers.
apps/graphics/twm4nx: Add CNxterm to the build. It is a long way from compiling.