Avoid inheritance from std::iterator

Instead of inheriting from the deprecated std::iterator
template, define the member typedefs needed for
std::iterator_traits directly.

Closes #1131.

Author: pah

include/rapidjson/document.h

@@ -45,7 +45,7 @@ RAPIDJSON_DIAG_OFF(terminate) // ignore throwing RAPIDJSON_ASSERT in RAPIDJSON_N
 #endif // __GNUC__
 
 #ifndef RAPIDJSON_NOMEMBERITERATORCLASS
-#include <iterator> // std::iterator, std::random_access_iterator_tag
+#include <iterator> // std::random_access_iterator_tag
 #endif
 
 #if RAPIDJSON_HAS_CXX11_RVALUE_REFS
@@ -98,16 +98,13 @@ struct GenericMember {
     \see GenericMember, GenericValue::MemberIterator, GenericValue::ConstMemberIterator
  */
 template <bool Const, typename Encoding, typename Allocator>
-class GenericMemberIterator
-    : public std::iterator<std::random_access_iterator_tag
-        , typename internal::MaybeAddConst<Const,GenericMember<Encoding,Allocator> >::Type> {
+class GenericMemberIterator {
 
     friend class GenericValue<Encoding,Allocator>;
     template <bool, typename, typename> friend class GenericMemberIterator;
 
     typedef GenericMember<Encoding,Allocator> PlainType;
     typedef typename internal::MaybeAddConst<Const,PlainType>::Type ValueType;
-    typedef std::iterator<std::random_access_iterator_tag,ValueType> BaseType;
 
 public:
     //! Iterator type itself
@@ -117,12 +114,21 @@ class GenericMemberIterator
     //! Non-constant iterator type
     typedef GenericMemberIterator<false,Encoding,Allocator> NonConstIterator;
 
+    /** \name std::iterator_traits support */
+    //@{
+    typedef ValueType      value_type;
+    typedef ValueType *    pointer;
+    typedef ValueType &    reference;
+    typedef std::ptrdiff_t difference_type;
+    typedef std::random_access_iterator_tag iterator_category;
+    //@}
+
     //! Pointer to (const) GenericMember
-    typedef typename BaseType::pointer         Pointer;
+    typedef pointer         Pointer;
     //! Reference to (const) GenericMember
-    typedef typename BaseType::reference       Reference;
+    typedef reference       Reference;
     //! Signed integer type (e.g. \c ptrdiff_t)
-    typedef typename BaseType::difference_type DifferenceType;
+    typedef difference_type DifferenceType;
 
     //! Default constructor (singular value)
     /*! Creates an iterator pointing to no element.