eliminate queue_clears or queue_draws where we know that expose events

eliminate queue_clears or queue_draws where we know that expose events

Wed Jan 13 13:28:00 1999  Tim Janik  <timj@gtk.org>

        * gtk/gtkwidget.c: eliminate queue_clears or queue_draws where we know
        that expose events will be generated.
        (gtk_widget_map): only queue_draw for NO_WINDOW widgets.
        (gtk_widget_unmap): only queue_clear_child for NO_WINDOW widgets.
        (gtk_widget_size_allocate): we don't need a queue_clear on changing
        allocations of !NO_WINDOW widgets, we do still need a full redraw for
        them though.

        * gtk/gtklabel.c (gtk_label_set_text): check whether the new string
        actually differs from the original.