remove use of std::iterator

iterator/infix.hpp

@@ -27,8 +27,14 @@ namespace cruft::iterator {
         class CharT = char,
         class Traits = std::char_traits<CharT>
     >
-    class infix_iterator : public std::iterator<std::output_iterator_tag, void, void, void, void> {
+    class infix_iterator {
     public:
+        using iterator_category = std::output_iterator_tag;
+        using value_type = void;
+        using difference_type = void;
+        using reference = void;
+        using pointer = void;
+
         using char_type    = CharT;
         using traits_type  = Traits;
         using ostream_type = std::basic_ostream<char_type, traits_type>;

string.hpp

@@ -133,12 +133,14 @@ namespace cruft {
         { ; }
 
 
-        struct iterator : public std::iterator<
+        struct iterator {
-            std::forward_iterator_tag,
-            value_type,
-            std::size_t
-        > {
         public:
+            using iterator_category = std::forward_iterator_tag;
+            using value_type = tokeniser::value_type;
+            using difference_type = std::size_t;
+            using pointer = value_type*;
+            using reference = value_type&;
+
             iterator  operator++ (int)
             {
                 iterator res(*this);