small bug in Axes.add_artist method

Hi,

I found a small bug in matplotlib.axes.Axes.add_artist method. matplotlib.artist.Artist.set_axes method is called twice.

def add_artist(self, a):
         '''
         Add any :class:`~matplotlib.artist.Artist` to the axes.

         Returns the artist.
         '''
         * a.set_axes(self) *
         self.artists.append(a)
         self._set_artist_props(a)
         a.set_clip_path(self.patch)
         a._remove_method = lambda h: self.artists.remove(h)
         return a

def _set_artist_props(self, a):
         'set the boilerplate props for artists added to axes'
         a.set_figure(self.figure)
         if not a.is_transform_set():
             a.set_transform(self.transData)

         * a.set_axes(self) *

matplotlib version: 0.99.1.1

Regards,

Yann