Free the linked polygon.

After reading the FFI literature closely, it may be wise to use
the built-in function from H3 to destroy linked polygons.

We may avoid a memory leak this way.

Author: seanhandley

lib/h3/bindings/private.rb

@@ -8,6 +8,7 @@ module Private
       extend H3::Bindings::Base
 
       attach_function :compact, [H3IndexesIn, H3IndexesOut, :size], :bool
+      attach_function :destroy_linked_polygon, :destroyLinkedPolygon, [LinkedGeoPolygon], :void
       attach_function :geo_to_h3, :geoToH3, [GeoCoord, Resolution], :h3_index
       attach_function :h3_indexes_from_unidirectional_edge,
                       :getH3IndexesFromUnidirectionalEdge,

lib/h3/regions.rb

@@ -142,6 +142,8 @@ def h3_set_to_linked_geo(h3_indexes)
       Bindings::Private.h3_set_to_linked_geo(h3_set, h3_indexes.size, linked_geo_polygon)
 
       extract_linked_geo_polygon(linked_geo_polygon).first
+    ensure
+      Bindings::Private.destroy_linked_polygon(linked_geo_polygon)
     end
 
     private