This patch reworks polygon_ring_appender to avoid some cases that caused
massive slowness. This involved doing 2 main things:

1. The `isIn` check has been reworked to avoid a dependency on OGR and
instead the winding number algorithm has been implemented directly. The
code itself was based on the reference code at geomalgorithms.com

2. Rather than sort all the rings in the destructor, the `addLine`
function has been reworked to put each new ring in the correct position
as it is added. To enable this, the Ring class was reworked to hold a
vector of child instances directly, effectively building a tree of
rings. Then in the destructor, we can simply walk the tree and write out
every other level as a polygon.