If additional areas got invalidated, don't try to add them to the paint

If additional areas got invalidated, don't try to add them to the paint

        * gtk/gtktextview.c (gtk_text_view_paint): If additional areas got
        invalidated, don't try to add them to the paint region: in an expose
        handler, we cannot paint outside the area that was passed in, since
        drawing will be clipped. So stealing the update region from the
        window causes lost draws.
        Patch by Owen Taylor

svn path=/trunk/; revision=22442