complibs/ppl: Fix build of ppl 0.11.2 with gmp 5.1 and later

The fix is backported from
http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commitdiff;h=9f843aecc23981aec6ed1eaa8be06e6786a47f0d.

Signed-off-by: Bernhard Walle <bernhard@bwalle.de>
Message-Id: <9a012bed87b494cfe0d4.1386503894@euler.fritz.box>
Patchwork-Id: 298789

#!/bin/sh

set -e

printf "Running autoconf...\n"

autoconf -Wall --force

printf "Done. You may now run:\n    ./configure\n"