bug#58464: 28.1; browse-url-emacs doesn't work for local files on Windows

[Eli Zaretskii]

> From: Pascal Quesseveur <pquessev@gmail.com>
> Date: Wed, 12 Oct 2022 08:43:15 +0200
> 
> 
> emacs -Q
> (browse-url-emacs "file://C:/Windows/win.ini") -> Emacs hangs, nothing
> is displayed, C-g
> (browse-url-emacs "file:///C:/Windows/win.ini") -> file content is
> displayed, Message buffer contains:
> 
> File exists, but cannot be read
> #<buffer win.ini</Windows>>

With Emacs 29, I get a different message:

  Use M-x make-directory RET RET to create the directory and its parents

That's because the file's name and its default-directory are
incorrect:

  M-: buffer-file-name RET
   => X:/C:/Windows/win.ini
  M-: default-directory RET
   => X:/C:/Windows/

(where X is the driver letter of what happens to be the current drive
when I invoke Emacs).