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

[Tino Calancha]

> Thanks, but I'm afraid this is not necessarily TRT.  You simply revert
> part of Stefan's change for some configurations, but I don't
> understand why not setting windows_or_buffers_changed affects Lucid,
> but not GTK.  Did you succeed in understanding the reason?

I don't know the reason.  For some reason, Stefan optimisation 
affects Lucid; probably he did not test his patch for that 
configuration.

If someone wants to dig deeper, it is very welcome; if nobody can, 
please, consider applying this simple patch.
I have been suffering this bug for months; until I realized I was able to
workaround getting a new frame, I was just closing the Emacs session
with dozens of visited buffers :-|

> And btw, why do you also add this for non-toolkit builds: did you see
> the same problem in that configuration?
I have reproduced the bug with both flags
 --with-x-toolkit=no
and 
--with-x-toolkit=lucid

I am just trying to cover in the patch all scenario where I have 
reproduced the bug; I can not test other configurations.
How about in Windows? Have you seen this bug?