Added the new reference data types.

Added the forward declaration of all classes.

include/opendrive_common.h

@@ -5,6 +5,20 @@
 #define DEFAULT_SCALE_FACTOR      1.0
 #define DEFAULT_MIN_ROAD_LENGTH   0.1
 
+#include <map>
+
+class COpendriveLane;
+class COpendriveRoadNode;
+class COpendriveRoadSegment;
+class COpendriveSignal;
+class COpendriveObject;
+class COpendriveRoad;
+class COpendriveLink;
+
+typedef std::map<COpendriveRoadNode *,COpendriveRoadNode *> node_up_ref_t;
+typedef std::map<COpendriveLane *,COpendriveLane *> lane_up_ref_t;
+typedef std::map<COpendriveRoadSegment *,COpendriveRoadSegment *> segment_up_ref_t;
+
 typedef struct
 {
   double s;