bug#49466: 28.0.50; C-<mouse-2> is undefined

[Eli Zaretskii <eliz@gnu.org>]

> From: Juri Linkov <juri@linkov.net>
> Date: Thu, 08 Jul 2021 20:36:22 +0300
> 
> The Info manual says in (info "(emacs) Menu Mouse Clicks")
> 
>   ‘C-mouse-2’
>        This menu contains entries for examining faces and other text
>        properties, and well as for setting them (the latter is mainly
>        useful when editing enriched text; *note Enriched Text::).
> 
> But clicking C-mouse-2 signals the error:
> 
>   C-<mouse-2> is undefined
> 
> The above Info node has a link to the "Enriched Text" node
> where (info "(emacs) Editing Format Info") says:
> 
>   The easiest way to alter properties is with the ‘Text Properties’ menu.
>   You can get to this menu from the ‘Edit’ menu in the menu bar (*note
>   Menu Bar::), or with ‘C-mouse-2’ (*note Menu Mouse Clicks::).
> 
> However, ‘C-mouse-2’ fails even in enriched-mode,
> e.g. after visiting etc/enriched.txt.
> 
> Also the documented ‘Text Properties’ menu
> is not displayed in enriched-mode.
> 
> PS: There is also this comment in lisp/mouse.el,
> maybe it should be removed:
> 
>   ;; C-down-mouse-2 is bound in facemenu.el.

That's because that binding was removed as part of butchering
facemenu.el in Emacs 28.