* src/glade-property.[ch]: Added glade_property_[push/pop]_superuser()

	* src/glade-command.c: refined set_property_execute() and started using
	  glade_property_push/pop_superuser().

	* src/glade-project.c: super-user property mode at load time.

	* src/glade-fixed.c: Added "can-resize" property

	* src/glade-widget-class.c: Made sure to parse a "Fixed" if there are no
	  other child tags.

	* src/glade-gtk.c, widgets/gtk+.xml.in: Implemented drag on GtkBox children