any cleanup handler.
(__libc_cleanup_region_end): Do nothing if start's DOIT arg was zero.
(__libc_cleanup_end): Likewise.
+ * sysdeps/generic/bits/libc-lock.h: Same changes.
* stdio-common/vfscanf.c (LOCK_STREAM): Pass new arg.
* stdio-common/vfprintf.c (buffered_vfprintf, vfprintf): Likewise.
* sysdeps/mach/hurd/bits/stdio-lock.h (_IO_cleanup_region_start):