bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: 22493@debbugs.gnu.org
> Date: Fri, 05 Feb 2016 18:34:44 +1100
> 
> There is no waiting in the GnuTLS library during negotiation.  It is
> fully asynchronous.  If any action blocks, it will return, and we can
> proceed later.  It works, seen from the application side, as any other
> network connection.

The _waiting_ is asynchronous.  The processing cannot be, because
GnuTLS doesn't start any threads.