bug#30364: 26.0.91; thread crash on macos

[Eli Zaretskii]

> Cc: 30364@debbugs.gnu.org, alan@idiocy.org, npostavs@gmail.com,
>  npostavs@users.sourceforge.net
> From: Daniel Colascione <dancol@dancol.org>
> Date: Mon, 19 Feb 2018 09:29:49 -0800
> 
> What about just dedicating a thread to GC?

If having several threads with 8MB of stack is asking for trouble,
then doing GC in a dedicated thread could be a better solution.

But I personally am undecided whether we should go that way as long as
threads are used as they are today (read: not used at all, AFAIK).
I'd suggest to wait until we see serious packages appear that are
based on Lisp threads, because if they never appear, we could declare
this experiment as failed, and then a separate GC thread might be just
a liability.