replaced pragma once with classic defines to omit warnings in gcc

Point.h

@@ -1,4 +1,5 @@
-#pragma once
+#ifndef POINT_H
+#define POINT_H
 
 class Point
 {
@@ -51,3 +52,4 @@ public:
         return (x() == other.x() && y() == other.y());
     }
 };
+#endif // POINT_H

Quickhull.h

@@ -1,4 +1,5 @@
-#pragma once
+#ifndef QUICKHULL_H
+#define QUICKHULL_H
 
 #include <list>
 #include <bits/stdc++.h>  // For INT_MIN & INT_MAX
@@ -150,3 +151,4 @@ private:
         get_hull_with_line(left_of_line2, output, new_line2);
     }
 };
+#endif // QUICKHULL_H

Triangle.h

@@ -1,4 +1,5 @@
-#pragma once
+#ifndef TRIANGLE_H
+#define TRIANGLE_H
 
 #include "Point.h"
 #include "Line.h"
@@ -35,3 +36,4 @@ public:
         return m_l3;
     }
 };
+#endif // TRIANGLE_H