alloc_traits.h (__alloc_traits::difference_type): Define.

	* include/ext/alloc_traits.h (__alloc_traits::difference_type):
	Define.

From-SVN: r186673

libstdc++-v3/ChangeLog

 2012-04-22  Jonathan Wakely  <jwakely.gcc@gmail.com>
 
+	* include/ext/alloc_traits.h (__alloc_traits::difference_type):
+	Define.
+
+2012-04-22  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
 	PR libstdc++/53027
 	* include/bits/ptr_traits.h (pointer_traits::rebind): Make public.
 	* testsuite/20_util/pointer_traits/requirements/typedefs.cc: Check

libstdc++-v3/include/ext/alloc_traits.h

@@ -99,6 +99,7 @@ template<typename _Alloc>
     typedef typename _Base_type::pointer            pointer;
     typedef typename _Base_type::const_pointer      const_pointer;
     typedef typename _Base_type::size_type          size_type;
+    typedef typename _Base_type::difference_type    difference_type;
     // C++0x allocators do not define reference or const_reference
     typedef value_type&                             reference;
     typedef const value_type&                       const_reference;
@@ -170,6 +171,7 @@ template<typename _Alloc>
     typedef typename _Alloc::reference              reference;
     typedef typename _Alloc::const_reference        const_reference;
     typedef typename _Alloc::size_type              size_type;
+    typedef typename _Alloc::difference_type        difference_type;
 
     static pointer
     allocate(_Alloc& __a, size_type __n)