[matplotlib-devel] wx scroll wheel

Hi,

I added support for scroll wheel events in wx.  This includes
a new attribute event.step since the wx mouse wheel event
reports larger steps when scrolling faster.  I don't see
how to check step in gtk, so I set step to +1 and -1 for up 
and down.

Can someone with gtk please run the following to make sure
I didn't break anything:

    examples/pylab_examples/image_slices_viewer.py


Thanks,

	- Paul