2014-07-22-21.35.55: src/lib/x-kit/widget/xkit/theme/packed/default/look/widget-imp.pkg: Packed_Widget_Option: Changed PACKED_WIDGET_CALLBACK from  Packed_Widget -> Void  to  Null_Or(Packed_Widget) -> Void  so that it could be used at shutdown to tell apps our packed_widget ports are no longer valid, as well as being used at startup to give our packed_widget ports to interested app code.