axis tick_top, tick_bottom behavior

Hi Everyone, The x axis can draw ticks on the top and/or

    > the bottom of the window. The default is both, with
    > ticklabels on the bottom. xaxis.tick_top will cause ticks
    > and labels to draw only on the top, tick_bottom will do
    > the same on the bottom. But if I make such a change, there
    > is no xaxis method to draw ticks (and maybe labels) on
    > both the top and the bottom, if I want to undo the
    > changes.

If noone responds with a -1 on these changes, go ahead and make them.
Be sure and update the API_CHANGES document and make sure that
examples/ still works (you may need to look at
pylab.twinx to insure that it is consistent with your changes).