fix first column and firt line not drawable

- within() method should include first point and exclude last.

java/org/artisanlogiciel/games/maze/Position.java

@@ -92,7 +92,8 @@ public class Position
             }
     }
 
+    /** WARNING [(a,b),(width,height)[ */
     public boolean within(int a, int b, int width, int height) {
-        return ((x > a) && (x < width) && (y > b) && (y < height));
+        return ((x >= a) && (x < width) && (y >= b) && (y < height));
     }
 }