Tests adopting asio code changes for asio 1.25.0.

include/boost/beast/core/detail/work_guard.hpp

@@ -34,9 +34,9 @@ struct select_work_guard
 template<class Executor>
 struct execution_work_guard
 {
-    using executor_type = decltype(
-        net::prefer(std::declval<Executor const&>(),
-            net::execution::outstanding_work.tracked));
+    using executor_type = typename std::decay<decltype(
+         net::prefer(std::declval<Executor const&>(),
+            net::execution::outstanding_work.tracked))>::type;
 
     execution_work_guard(Executor const& exec)
     : ex_(net::prefer(exec, net::execution::outstanding_work.tracked))

include/boost/beast/core/stream_traits.hpp

@@ -111,7 +111,7 @@ using executor_type =
 #else
 template<class T>
 using executor_type =
-    decltype(std::declval<T&>().get_executor());
+    typename std::decay<decltype(std::declval<T&>().get_executor())>::type;
 #endif
 
 /** Determine if `T` has the `get_executor` member function.