Pull up following revision(s) (requested by kamil in ticket #1176):
external/gpl3/gcc/dist/gcc/cp/cfns.h: revision 1.2
external/gpl3/gcc/dist/gcc/cp/except.c: revision 1.2
external/gpl3/gcc/dist/gcc/cp/Make-lang.in: revision 1.6
external/gpl3/gcc/dist/gcc/cp/cfns.gperf: revision 1.2
Fix building GCC-5.3 with GCC-6.1
Cherry-pick upstream patch:
From 1e5f1089dec3af328fd03125d6778f666d0bd4e4 Mon Sep 17 00:00:00 2001
From: edlinger <edlinger@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 25 Feb 2016 15:33:50 +0000
Subject: [PATCH] 2016-02-25  Bernd Edlinger  <bernd.edlinger%hotmail.de@localhost>
        Backported from mainline
        2016-02-19  Jakub Jelinek  <jakub%redhat.com@localhost>
                    Bernd Edlinger  <bernd.edlinger%hotmail.de@localhost>
        * Make-lang.in: Invoke gperf with -L C++.
        * cfns.gperf: Remove prototypes for hash and libc_name_p
        inlines.
        * cfns.h: Regenerated.
        * except.c (nothrow_libfn_p): Adjust.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-5-branch@233720 138bc75d-0d04-0410-961f-82ee72b054a4
Verified to work with GCC 5.3 and 6.1.

(snj)