Add a new type in Implicit_multi_domain_to_labeled_function_wrapper.

Add the type definition Function_vector in the wrapper
Implicit_multi_domain_to_labeled_function_wrapper.

Mesh_3/include/CGAL/Mesh_3/Implicit_to_labeled_function_wrapper.h

@@ -145,6 +145,7 @@ public:
   typedef int                     return_type;
   typedef typename BGT::Point_3   Point_3;
   typedef Function_               Function;
+  typedef std::vector<Function_>   Function_vector;
 
 private:
 	std::vector<Function> funcs;