bug#12697: 24.2; Emacs crashes when using it as the commit editor for git

[Eli Zaretskii <eliz@gnu.org>]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: matthew@mattleach.net,  12697@debbugs.gnu.org
> Date: Mon, 22 Oct 2012 19:39:55 +0200
> 
> >> now that emacs no longer puts itself and the terminal into its own
> >> process group.
> >
> > Did we have good reason to stop doing that?
> 
> IMHO no.  All the BSD_PGRPS stuff was removed on the premise that it
> wasn't used any more, but disabling BSD_PGRPS in s/gnu-linux.h was
> already questionable.

Come think about it, why not stop depending on SIGINT for quitting?
We already do that in GUI session (AFAIU), so why should TTY frames be
different?  We could just detect C-g in the SIGIO handler, no?

If this makes sense, then this whole issue would go away.  Of course,
we will then lose the "emergency exit" feature, but since core dumps
are reportedly disabled on many systems anyway, that doesn't sound
like too much of a loss, and GUI sessions already cannot use it
anyway.