bug#34179: 27.0.50; message hangs when buffer with process visible

[Eli Zaretskii]

> Date: Fri, 25 Jan 2019 17:51:53 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: michael_heerdegen@web.de, 34179@debbugs.gnu.org
> 
>  > In any case, it is way too easy to do in functions called from
>  > run_window_change_functions something that sets
>  > windows_or_buffers_changed, so automatically retrying redisplay based
>  > on that variable after run_window_change_functions returns is IMO
>  > dangerous.
> 
> But what would be the alternatives?

Just leaving the job for the next redisplay cycle.  IOW, removing the
windows_or_buffers_changed from the condition under which we "goto retry".