Zoning: Cache expensive zoning overlay values

src/openttd.cpp

@@ -69,6 +69,7 @@
 #include "viewport_func.h"
 #include "thread/thread.h"
 #include "bridge_signal_map.h"
+#include "zoning.h"
 
 #include "linkgraph/linkgraphschedule.h"
 #include "tracerestrict.h"
@@ -348,6 +349,8 @@ static void ShutdownGame()
 	FreeSignalPrograms();
 	FreeSignalDependencies();
 
+	ClearZoningCaches();
+
 	/* No NewGRFs were loaded when it was still bootstrapping. */
 	if (_game_mode != GM_BOOTSTRAP) ResetNewGRFData();