replaced some gtk_object_data_force_id with g_quark_from_static_string

replaced some gtk_object_data_force_id with g_quark_from_static_string

Fri Jun 19 03:29:04 1998  Tim Janik  <timj@gtk.org>

        * gtk/gtkaccelgroup.c:
        * gtk/gtkbindings.c:
        * gtk/gtkcontainer.c:
        * gtk/gtkitemfactory.c:
        * gtk/gtkobject.c:
        * gtk/gtksignal.c:
        * gtk/gtkwidget.c: replaced some gtk_object_data_force_id with
        g_quark_from_static_string calls to save memory.

        * gtk/gtkobject.c (gtk_object_set_data_by_id_full): invoke the destroy
        function _after_ the new data has been setup.
        minor changes to object data functions to feature the GQuark type.