remove fill-winding

Should we remove `fill-winding`? When would this be used?

@kkaefer @mourner @nickidlugash 

Fill winding currently determines how overlapping polygon areas get treated. In the current spec, the even-odd option would mean that areas covered by an even number of polygons would get counted as not being within the polygon.

![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Even-odd_and_non-zero_winding_fill_rules.png/1258px-Even-odd_and_non-zero_winding_fill_rules.png)