Triangulation_2: Initialize to avoid warning

Triangulation_2/include/CGAL/Constrained_triangulation_plus_2.h

@@ -649,7 +649,7 @@ public:
 	++it){
       if(! is_subconstraint(*it, *succ)){ // this checks whether other constraints pass
 	Face_handle fh;
-	int i;
+	int i = -1; // this will be set by is_edge() below. Without initialization we get a warning
         CGAL_triangulation_assertion_code(bool b =)
           Triangulation::is_edge(*it, *succ, fh, i);
 	CGAL_triangulation_assertion(b);