[tuple.general] Move tuple_element_t definition after last specialization of tuple_element.

Author: Stefanus Du Toit

source/utilities.tex

@@ -1021,11 +1021,11 @@
   template <size_t I, class T> class tuple_element<I, volatile T>;
   template <size_t I, class T> class tuple_element<I, const volatile T>;
 
+  template <size_t I, class... Types> class tuple_element<I, tuple<Types...> >;
+
   template <size_t I, class T>
     using tuple_element_t = typename tuple_element<I, T>::type;
 
-  template <size_t I, class... Types> class tuple_element<I, tuple<Types...> >;
-
   // \ref{tuple.elem}, element access:
   template <size_t I, class... Types>
     constexpr tuple_element_t<I, tuple<Types...>>&