Extracted from this commit without the ChangeLog to avoid conflicts:
http://git.savannah.gnu.org/cgit/smalltalk.git/commit/?id=72ada189aba0283c551ead16635c1983968080b8

The upstream commit message is
From 72ada189aba0283c551ead16635c1983968080b8 Mon Sep 17 00:00:00 2001
From: Holger Hans Peter Freyther <holger@moiji-mobile.com>
Date: Sat, 7 Nov 2015 18:09:31 +0100
Subject: libgst: Add alternative multiplication overflow check

Apple clang on OSX and the version on FreeBSD optimize the
multiplication check away. Clang introduced a family of
builtins to do the multiplication and check for the overflow
and GCC made the API usable. For clang we would need to know
if intptr_t is of type int, long int, long long int and
then use the smul, smull smulll.
Luckily clang is adopting the better interface and this is
what we are starting to use now. This means the new code
will be used on GCC5 (and later) and some future versions of
clang.

2015-11-07  Holger Hans Peter Freyther  <hol</td></tr></table>
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<tr><th>author</th><td>Ricardo Wurmus &lt;rekado@elephly.net&gt;</td><td class='right'