bug#20891: emacs: Back off if .doc is not an Office document

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Lars Ingebrigtsen <larsi@gnus.org>,  era+emacs@iki.fi,
>   20891@debbugs.gnu.org,  stefan@marxist.se
> Date: Thu, 14 Nov 2019 16:06:36 +0100
> 
> Today we go: ".doc extension -> show an image of the contents of the
> file"

Where do we have the code or data which does that?

> which is manifestly the wrong thing to do for a non-doc file. If
> we do the signature recognition, those files which are not recognized
> end up in (probably) fundamental-mode

That's OK, but I'm still missing the code which makes this happen.
E.g., I just did "C-x C-f foo.doc RET" and got a buffer in Fundamental
mode.