Fixes some issues with our winding # calculation which would cause
incorrect results for hitTest.
* The convention for handling an intersection at endpoints was
not the same between lines and bezier curves.
* The bezier curve winding # function was not properly handling
some cases where the curve was strictly y-monotonic.
* Simplify the code a bit so that ray-curve intersections are
returned in a consistent order based on upward/downward crossing.
Mike Welsh