bug#40375: 27.0.50; yank unexpectedly depends on progn

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  40375@debbugs.gnu.org,
>   schwab@linux-m68k.org
> Date: Mon, 13 Apr 2020 18:16:26 -0400
> 
> Markus Triska <triska@metalevel.at> writes:
> 
> > Please consider documenting this in the description of `yank'. Other
> > than that, I consider this issue resolved.
> 
> Does this look okay?  (modulo a fill-paragraph which I've held off on
> just to make the patch easier to read)

Thanks, I fixed this in a slightly different manner (as just
mentioning interprogram-paste-function may not be accurate enough).