chmod: fix use of uninitialized var if -v

chmod: fix use of uninitialized var if -v

Problem reported by Michael Debertol (Bug#50070).
* NEWS: Mention the fix.
* src/chmod.c (struct change_status): New struct, replacing the
old enum Change_status.  All uses changed.
(describe_change): Distinguish between cases depending on
whether 'stat' or its equivalent succeeded.  Report a line
of output even if 'stat' failed, as that matches the documentation.
Rework to avoid casts.
(process_file): Do not output nonsense modes computed from
uninitialized storage, removing a couple of IF_LINTs.  Simplify by
defaulting to CH_NO_STAT.