Updated v2_0_cpp_visitor (markdown)

v2_0_cpp_visitor.md

@@ -26,6 +26,7 @@ struct visitor {
     bool end_map();
     void parse_error(size_t parsed_offset, size_t error_offset);
     void insufficient_bytes(size_t parsed_offset, size_t error_offset);
+    bool referenced() const; // Only when you want to use the visitor with a parser
 };
 ```
 
@@ -91,7 +92,6 @@ struct null_visitor {
     }
     void insufficient_bytes(size_t /*parsed_offset*/, size_t /*error_offset*/) {
     }
-    bool referenced() const; // Only when you want to use the visitor with a parser
 };
 ```