* app/interface.c: hinted the window manager that the toolbox window
is a toolbox window. Not that my (fairly default configuration)	sawfish
cares, but other NETWM compliant WMs may.	* app/commands.c: 	*
app/defaults.c: 	* app/dia-props.c:	* app/filedlg.c: 	*
app/interface.c: 	* app/layer_dialog.c: 	* app/linewidth_area.c:
* app/properties.c: 	* app/sheets_dialog.c: 	* app/splash.c: 	The
GTK doc says to avoir gtk_window_set_wmclass() and
gtk_window_set_policy(), and use gtk_window_set_role() and
gtk_window_set_resizable(), respectively.		* app/preferences.c:
(prefs_create_dialog):	* app/preferences.h:	* app/display.c:
(display_set_active):	Added a preference to have the toolbox hover over
diagram windows.