Update comment for local db entry creation

Mention mtree files do not need creation in addtion to install files.

Signed-off-by: Allan McRae <allan@archlinux.org>

lib/libalpm/be_local.c

@@ -990,8 +990,8 @@ int _alpm_local_db_write(alpm_db_t *db, alpm_pkg_t *info, alpm_dbinfrq_t inforeq
 		fp = NULL;
 	}
 
-	/* INSTALL */
-	/* nothing needed here (script is automatically extracted) */
+	/* INSTALL and MTREE */
+	/* nothing needed here (automatically extracted) */
 
 cleanup:
 	umask(oldmask);