bug#10398: [PATCH] Use real vfork under Cygwin: it's fine these days

[Eli Zaretskii]

> From: Lars Magne Ingebrigtsen <larsi@gnus.org>
> Cc: 10398@debbugs.gnu.org, Eli Zaretskii <eliz@gnu.org>
> Date: Wed, 11 Apr 2012 01:26:56 +0200
> 
> Daniel Colascione <dancol@dancol.org> writes:
> 
> > In Cygwin 1.7, vfork is an alias for fork.  The vfork the #define in
> > cygwin.h was protecting against is gone.  It's better to use vfork now
> > so that when Cygwin gains a new, working vfork, we use it
> > automatically.
> 
> [...]
> 
> > -/* vfork() interacts badly with setsid(), causing ptys to fail to
> > -   change their controlling terminal */
> > -#define vfork fork
> 
> Sounds sensible to me, but I'm no exactly (ahem) a Cygwin expert.
> 
> Eli, what do you think?

Not that _I_ am a Cygwin expert, but isn't it safer to do that only
for Cygwin 1.7 and later?  Ken, WDYT?