d.vect.chart: use standardized option for columns

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@57591 15284696-431f-4ddb-bdfa-cd5b030d7da7

display/d.vect.chart/main.c

@@ -84,11 +84,8 @@ int main(int argc, char **argv)
     ctype_opt->description = _("Chart type");
     ctype_opt->guisection = _("Chart properties");
 
-    columns_opt = G_define_option();
-    columns_opt->key = "columns";
-    columns_opt->type = TYPE_STRING;
+    columns_opt = G_define_standard_option(G_OPT_DB_COLUMNS);
     columns_opt->required = YES;
-    columns_opt->multiple = YES;
     columns_opt->description = _("Attribute columns containing data");
 
     sizecol_opt = G_define_option();