vlib: cosmetics in dox strings (dig_struct.c)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@47880 15284696-431f-4ddb-bdfa-cd5b030d7da7

include/vect/dig_structs.h

@@ -1133,7 +1133,9 @@ struct Map_info
     */
     int support_updated;
     /*!
-      \brief Sequential read (level 1)
+      \brief Sequential read (level 1) - see Vect_read_next_line()
+
+      Note: Line id starts with 1
     */
     plus_t next_line;