math: added OPT_BOX2 type

include/math/box2.h

@@ -30,6 +30,7 @@
 #include <math/vector2d.h>
 #include <limits>
 
+#include <boost/optional.hpp>
 
 /**
  * Class BOX2
@@ -467,6 +468,8 @@ public:
 typedef BOX2<VECTOR2I>    BOX2I;
 typedef BOX2<VECTOR2D>    BOX2D;
 
+typedef boost::optional<BOX2I> OPT_BOX2I;
+
 // FIXME should be removed to avoid multiple typedefs for the same type
 typedef BOX2D             DBOX;