complibs/ppl: Fix build of ppl 0.11.2 with gcc 4.9

From: Roberto Bagnara <bagnara@cs.unipr.it>
Date: Tue, 29 Apr 2014 19:51:43 +0000 (+0200)
Subject: Added missing inclusions. Use std::ptrdiff_t.
X-Git-Url: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl%2Fppl.git;a=commitdiff;h=61d4e14dfd9f1121e9b4521dead5728b2424dd7c

Added missing inclusions. Use std::ptrdiff_t.
(Thanks to Paulo Cesar Pereira de Andrade.)

Signed-off-by: Bernhard Walle <bernhard@bwalle.de>
Message-Id: <5632a171e7c1dc4c0fb5.1399806148@euler.fritz.box>
Patchwork-Id: 347777

 hg