Add point in polygon test using winding counting method

[kurtlawrence]

Fixes #172

Since this method is different to the one defined, namely that it does not short-circuit, I have left the original.

[sebcrozet]

Thanks! I renamed the existing method to point_in_convex_poly2d (since it didn’t handle non-convex polygons anyway), so that your implementation can take the point_in_poly2d name.