From: Bernhard Walle <bernhard@bwalle.de>
Subject: Fix compilation with gcc 4.9 (ptrdiff_t errors)

This is a backport of following patch in ppl git

  commit 61d4e14dfd9f1121e9b4521dead5728b2424dd7c
  Author: Roberto Bagnara <bagnara@cs.unipr.it>
  Date:   Tue Apr 29 21:51:43 2014 +0200

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

---
 src/Congruence_System.defs.hh     |    3 ++-
 src/Constraint_System.defs.hh     |    3 ++-
 src/Generator_System.defs.hh      |    3 ++-
 src/Grid_Generator_System.defs.hh |    3 ++-
 4 files changed, 8 insertions(+), 4 deletions(-)

--- a/src/Grid_Generator_System.defs.hh
+++ b/src/Grid_Generator_System.defs.hh
@@ -30,6 +30,7 @@ site: http://www.cs.unipr.it/ppl/ . */
 #include "Variables_Set.types.hh"
 #include "Grid.types.hh"
 #include <iosfwd>
+#include <cstddef>
 
 namespace Parma_Polyhedra_Library {
 
@@ -267,7 +268,7 @@ public:
   class const_iterator
     : public std::iterator<std::forward_iterator_tag,
 			   Grid_Generator,
-			   ptrdiff_t,
+			   std::ptrdiff_t,
 			   const Grid_Generator*,
 			   const Grid_Generator&>,
       private Generator_System::const_iterator {
--- a/src/Congruence_System.defs.hh
+++ b/src/Congruence_System.defs.hh
@@ -33,6 +33,7 @@ site: http://www.cs.unipr.it/ppl/ . */
 #include "Grid.types.hh"
 #include "Grid_Certificate.types.hh"
 #include <iosfwd>
+#include <cstddef>
 
 namespace Parma_Polyhedra_Library {
 
@@ -235,7 +236,7 @@ public:
   class const_iterator
     : public std::iterator<std::forward_iterator_tag,
 			   Congruence,
-			   ptrdiff_t,
+			   std::ptrdiff_t,
 			   const Congruence*,
 			   const Congruence&> {
   public:
--- a/src/Constraint_System.defs.hh
+++ b/src/Constraint_System.defs.hh
@@ -33,6 +33,7 @@ site: http://www.cs.unipr.it/ppl/ . */
 #include "Congruence_System.types.hh"
 #include <iterator>
 #include <iosfwd>
+#include <cstddef>
 
 namespace Parma_Polyhedra_Library {
 
@@ -204,7 +205,7 @@ public:
   class const_iterator
     : public std::iterator<std::forward_iterator_tag,
 			   Constraint,
-			   ptrdiff_t,
+			   std::ptrdiff_t,
 			   const Constraint*,
 			   const Constraint&> {
   public:
--- a/src/Generator_System.defs.hh
+++ b/src/Generator_System.defs.hh
@@ -33,6 +33,7 @@ site: http://www.cs.unipr.it/ppl/ . */
 #include "Polyhedron.types.hh"
 #include "Poly_Con_Relation.defs.hh"
 #include <iosfwd>
+#include <cstddef>
 
 namespace Parma_Polyhedra_Library {
 
@@ -250,7 +251,7 @@ public:
   class const_iterator
     : public std::iterator<std::forward_iterator_tag,
 			   Generator,
-			   ptrdiff_t,
+			   std::ptrdiff_t,
 			   const Generator*,
 			   const Generator&> {
   public: