bug#42655: 27.1; iconify-frame on a Lucid build may stuck the frame

[Tino Calancha]

Eli Zaretskii <eliz@gnu.org> writes:

 
>> Naively, I can workaround this issue by checking for an iconified frame at
>> FocusIn:  this fixes this issue in both `emacs -Q` and my
>> custom Emacs session.
>
> That would be my next idea, so please go ahead and install this.  And
> thanks for all the footwork in investigating this issue.

Thank you for your guidance.  It was crucial.

Pushed fix into emacs-27 branch as commit
'Prevent from frozen frame after `C-z' in Lucid builds'
(3c4edfd85ee8f49e40715a400a1fc65950e07482)