Make List<>::Node not uncopyable

beast/intrusive/List.h

@@ -41,7 +41,7 @@ namespace detail
 // concurrently is required.
 //
 template <typename T, typename Tag>
-class ListNode : public Uncopyable
+class ListNode
 {
 private:
     typedef T value_type;

modules/beast_core/thread/DeadlineTimer.h

@@ -22,7 +22,9 @@
 
 /** Provides periodic or one time notifications at a specified time interval.
 */
-class DeadlineTimer : public List <DeadlineTimer>::Node
+class DeadlineTimer
+    : public List <DeadlineTimer>::Node
+    , public Uncopyable
 {
 public:
     /** Listener for a deadline timer.