bug#12327: Signal-handler cleanup for Emacs

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 07 Sep 2012 01:59:20 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> CC: lekktu@gmail.com, 12327@debbugs.gnu.org
> 
> > (Why are there still calls to 'signal', as opposed to 'sigaction', in
> > some parts of Emacs?)
> 
> Thanks for catching that.  Three of them were wrong -- a glitch when
> merging patches.  Fixed in trunk bzr 109922.
> 
> The other calls are setting signal handlers to SIG_DFL or SIG_IGN.
> For these, signal and sigaction do the same thing, so I left the
> calls alone, to minimize changes.  If it's better, for regularity
> purposes, to replace these 'signal' calls with 'sigaction' calls,
> that's an easy and simple change that I can do.

I think it's better to use a single family of functions, it makes the
code slightly easier to comprehend.

But I'm okay with leaving those calls to 'signal', if no one else
cares.  It just means that 'sys_signal' in the Windows sources will
have to be rewritten to call 'sigaction' internally (I left it alone
in revision 109919 because I thought it was on its way out).