* libio/genops.c (_IO_list_all_stamp): New variable.
(_IO_un_link): Bump _IO_list_all_stamp after removing from list.
(_IO_link): Likewise for insertion.
(flush_cleanup): New function.
(_IO_flush_all): Get list_all_lock and all individual locks for the
streams. Detect and handle changes to the _IO_list_all list.
(_IO_flush_all_linebuffered): Likewise.
* sysdeps/generic/bits/stdio-lock.h: Define
_IO_cleanup_region_start_noarg.
* sysdeps/mach/hurd/bits/stdio-lock.c: Likewise.
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