bug#53894: 27.2; Clipboard copy -> C-y -> M-y -> Same clipboard copy does not push to kill ring

[Eli Zaretskii]

> From: Ignacio Casso <ignaciocasso@hotmail.com>
> Cc: Lars Ingebrigtsen <larsi@gnus.org>, Eli Zaretskii <eliz@gnu.org>,
>  53894@debbugs.gnu.org
> Date: Mon, 28 Feb 2022 13:12:44 +0100
> 
> I have installed the development version of Emacs and made a first patch
> attempt, preserving the structure of the program as much as possible. I
> have not tested thoroughly, but it works for all the cases I have
> tried. I have attached it to this mail, and comment each change
> below. Let me know what you think.

Thanks.

My worry after skimming this is that you are making X-specific changes
in places that are used by non-X GUI environments and window-systems.
Can't we do all that entirely in X-specific code, so that the
probability of breaking other window-systems would be strictly zero?