Fix point-in-polygon for multiple polar rings.

Instead of detecting if any single polygon ring winds around a pole, we
consider the cumulative winding of all polygon rings together.  This is
consistent with the area calculation, which considers the cumulative
area total of all rings.

This fixes #1521: an issue with the Hammer Retroazimuthal projection,
which uses such a polygon with two rings, covering most of the globe.

In addition, drop the special handling of points at the south pole,
which might have been there to pass an incorrect test: a CCW triangle
touching the south pole, which was probably incorrectly thought to be
clockwise.  This fixes an issue with a “stripe” polygon rotated so that
a point is at the south pole, mentioned in #1453.