assert that the passed in arrow is always _UP or _DOWN, this catches false

assert that the passed in arrow is always _UP or _DOWN, this catches false

Fri Jan 25 14:03:36 2002  Tim Janik  <timj@gtk.org>

        * gtk/gtkspinbutton.c (gtk_spin_button_draw_arrow): assert
        that the passed in arrow is always _UP or _DOWN, this catches
        false invocations which lead to drawing artefacts.
        (start_spinning): likewise, i.e. sanity check the passed in arrow.
        (gtk_spin_button_button_release): fix arrow redrawing.
        (gtk_spin_button_button_press): must set click_child for
        button3 even if we don't take spinning action right away.

        * gtk/gtkspinbutton.h (struct _GtkSpinButton): document
        valid values for click_child.