Add comment: old schema is OC less category (abstract, struct, aux).

servers/slapd/schemaparse.c

@@ -68,7 +68,12 @@ parse_oc_old(
 	oc->oc_names = ch_calloc( 2, sizeof(char *) );
 	oc->oc_names[0] = ch_strdup( argv[1] );
 	oc->oc_names[1] = NULL;
+
 	if ( strcasecmp( oc->oc_names[0], "top" ) ) {
+		/*
+		 * no way to distinguish "auxiliary" from "structural"
+		 * This may lead to future problems.
+		 */
 		oc->oc_kind = LDAP_SCHEMA_STRUCTURAL;
 	}
 	for ( i = 2; i < argc; i++ ) {