bug#25183: 26.0.50; expanding quoted file name on w32

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Date: Mon, 12 Dec 2016 16:54:06 +0100
> 
> 
> Expanding a quoted file name works wrong on w32 systems. With Emacs
> running on ‘gnu/linux’, there is
> 
> (expand-file-name "/:~/path/./file")
> => "/:~/path/file"
> 
> This is correct. With Emacs running on ‘windows-nt’, there is
> 
> (expand-file-name "/:~/path/./file")
> => "/:c:/Users/lb01177/AppData/Roaming/path/file"

Try

   (expand-file-name "/:c:/~/path/./file")

expand-file-name needs to produce an absolute file name, and a file
name that begins with a "~" isn't.

IOW, I believe this is a feature.  If you think it isn't, please
explain why.