Change to which WKB representations SpatialPolygons convert to
SpatialPolygons objects now convert to either WKB Polygons or WKB
MultiPolygons
If each Polygons object in the SpatialPolygons object contains a
single Polygon object with only one exterior boundary then convert to
WKB Polygon, otherwise convert to WKB MultiPolygon
Previously SpatialPolygons were converted to WKB Polygon containing
multiple rings