iterator/iota: declare the iterator type first up

This means reduces the chances of mixing up inner/outer types, and
eliminates the use of the iterator typedef within teh container.

iterator/iota.hpp

@@ -24,24 +24,6 @@ namespace cruft::iterator {
     template <typename ValueT = std::size_t>
     class iota {
     public:
-        class iterator;
-
-        using value_type = ValueT;
-        using reference = ValueT&;
-        using const_reference = ValueT const&;
-        using const_iterator = iterator;
-        using iterator = iterator;
-        using difference_type = ssize_t;
-        using size_type = size_t;
-
-        iota ()
-            : m_total {}
-        { ; }
-
-        iota (value_type _total)
-          : m_total (_total)
-        { ; }
-
         class iterator {
         public:
             using iterator_category = std::random_access_iterator_tag;
@@ -78,6 +60,22 @@ namespace cruft::iterator {
             ValueT m_value;
         };
 
+        using value_type = ValueT;
+        using reference = ValueT&;
+        using const_reference = ValueT const&;
+        using const_iterator = iterator;
+        using iterator = iterator;
+        using difference_type = ssize_t;
+        using size_type = size_t;
+
+        iota ()
+            : m_total {}
+        { ; }
+
+        iota (value_type _total)
+          : m_total (_total)
+        { ; }
+
         iterator   begin (void) const { return iterator {}; }
         iterator   end   (void) const { return iterator {m_total}; }