bug#24897: 24.5; doc for `M' in Dired

[Eli Zaretskii]

> Date: Mon, 7 Nov 2016 11:28:52 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 24897@debbugs.gnu.org
> 
> > and if that is so, explaining the
> > Unix-style permission bits won't help a bit.
> 
> True enough for r and x, but not for w.  It is reasonable for a user
> on Windows to use `M' to make files read-only or writable.

But there's no "write" bit on Windows, at least not on the level on
which the 'M' command in Dired works on Windows.  So you cannot really
explain the w bit, either.

You need a completely separate description for Windows users.