Make checkpoint hashing faster!

src/Checkpoint.h

@@ -64,6 +64,6 @@ struct std::hash<Checkpoint>
 {
   std::size_t operator()(const Checkpoint&checkpoint)const
   {
-	return std::hash<int_fast64_t>()((((int_fast64_t)(*(int_fast32_t*)(&checkpoint.pos.x))<<32)|*(int_fast32_t*)(&checkpoint.pos.y)));
+	return (int_fast64_t)(*(int_fast32_t*)(&checkpoint.pos.x))<<32|*(int_fast32_t*)(&checkpoint.pos.y);
   }
 };