Move handler into wrapped_handler.

asio/include/asio/detail/wrapped_handler.hpp

diff --git a/asio/include/asio/detail/wrapped_handler.hpp b/asio/include/asio/detail/wrapped_handler.hpp
index 5b78afa..042bdb1 100644
--- a/asio/include/asio/detail/wrapped_handler.hpp
+++ b/asio/include/asio/detail/wrapped_handler.hpp
@@ -30,9 +30,9 @@
 public:
   typedef void result_type;
 
-  wrapped_handler(Dispatcher dispatcher, const Handler& handler)
+  wrapped_handler(Dispatcher dispatcher, Handler& handler)
     : dispatcher_(dispatcher),
-      handler_(handler)
+      handler_(ASIO_MOVE_CAST(Handler)(handler))
   {
   }