log transforms in new API

I have incorporated log transforms into the new axes API and committed
them to CVS. There are some minor issues to hammer out, eg, ticksizes
in log transforms (which was also a problem before), but its 97.5%

wx generated a nice looking log plot with log_demo.py with no changes
(cool!) but one bug was revealed

hunter:~/python/projects/matplotlib/examples> python log_demo.py -dWX
Traceback (most recent call last):
  File "/hunter/jdhunter/python/projects/matplotlib/matplotlib/backends/backend_wx.py", line 634, in _onSize
    self.bbox.set_bounds(0, 0, w, h)
NameError: global name 'w' is not defined

John Hunter