bug#51820: 29.0.50; process_pending_signals is almost useless without SIGIO

[Eli Zaretskii]

> Date: Sat, 13 Nov 2021 18:25:55 -0500
> Cc: 51820@debbugs.gnu.org, Eli Zaretskii <eliz@gnu.org>
> From: Ken Brown <kbrown@cornell.edu>
> 
> > In that case, perhaps someone using Cygwin (i.e., not me) could look into 
> > this. 
> > Evidently it has not been much of a practical problem all these years.
> 
> It's hard to know whether it's been a problem.  Maybe emacs would be more 
> responsive to C-g on Cygwin if we removed the #ifdef from handle_async_input. 
> My preference would be to try that (on master of course) and see if anything 
> breaks.
> 
> Eli, WDYT?

Sure, feel free to install such a change on master.  I don't know how
many Cygwin users track the Emacs master branch, but if there are more
than a couple, perhaps even provide a variable exposed to Lisp that
users could tweak to see the result without rebuilding and without
leaving the session.

Thanks.