minor spelling

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@50461 15284696-431f-4ddb-bdfa-cd5b030d7da7

include/vect/dig_structs.h

@@ -1169,7 +1169,7 @@ struct Map_info
       \brief Mapset name
     */
     char *mapset;
-    /* location and gisdbase is usefull if changed (v.proj or external apps) */
+    /* location and gisdbase is useful if changed (v.proj or external apps) */
     /*!
       \brief Location name
     */