Externalizing polygon shard detection (#146)

* Start of externalizing polygon shard detection

* Completely untested external quicksort

* Add unit test for external quicksort

* Remember to clean up temporary files

* Sort and scan the vertices

* Bring over more vertex logic

* Make nodes from vertices

* Checkpoint on switching over to global shared nodes

* Do the thing

* Revert unintended change to coalesced linestring behavior

* Take shared nodes into account in early simplification

* Let it do more sorting in memory

* Fix overnoding of collinear linestrings

* Remove duplicate nodes, since only duplicate vertices now matter

* Remember to delete temporary files

* Fix out of bounds memory access below, apparently

* Fix the actual undefined behavior

* Still running out of memory in one case. Find out where.

* Forgot the conditional

* Try again to make it not run out of memory

* Update version and changelog

Makefile

@@ -58,7 +58,7 @@ C = $(wildcard *.c) $(wildcard *.cpp)
 INCLUDES = -I/usr/local/include -I.
 LIBS = -L/usr/local/lib
 
-tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o
+tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o sort.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-enumerate: enumerate.o
@@ -73,7 +73,7 @@ tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpul
 tippecanoe-json-tool: jsontool.o jsonpull/jsonpull.o csv.o text.o geojson-loop.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
-unit: unit.o text.o
+unit: unit.o text.o sort.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-overzoom: overzoom.o mvt.o clip.o