Change header guard pragma once to more standard ifndef

Signed-off-by: Bensuperpc <bensuperpc@gmail.com>

include/astar/astar.hpp

@@ -3,7 +3,8 @@
  * MIT License
  */
 
-#pragma once
+#ifndef BEN_ASTAR_HPP
+#define BEN_ASTAR_HPP
 
 #include <algorithm>
 #include <cmath>
@@ -363,3 +364,5 @@ class AStarFast final : public AStarVirtual<CoordinateType, enableDebug> {
 };
 
 }  // namespace AStar
+
+#endif