Remove conditionals for ANSI-standard signals

[Eli Zaretskii]

> Date: Thu, 5 Jun 2014 09:10:14 -0700
> From: Doug Evans <xdje42@gmail.com>
> Cc: "gdb-patches@sourceware.org" <gdb-patches@sourceware.org>, Eli Zaretskii <eliz@gnu.org>
> 
> I can't see any sorting order to the places that have all the #ifdefs
> (common/signals.c in particular)

They are probably sorted in the order of their numerical values.

> and I wonder if it would be useful
> to put the non-#ifdef'd signals first with a comment explaining why
> they don't have #ifdefs.

Sounds like a good idea, indeed.