Fixes to support Asio changes (API Change):

This adjusts Beast's interfaces and implementation to match
the changes in Boost.Asio.

test/beast/core/tcp_stream.cpp

@@ -9,3 +9,37 @@
 
 // Test that header file is self-contained.
 #include <boost/beast/core/tcp_stream.hpp>
+
+#include <boost/beast/_experimental/unit_test/suite.hpp>
+
+namespace boost {
+namespace beast {
+
+class tcp_stream_test
+    : public beast::unit_test::suite
+{
+public:
+    using tcp = net::ip::tcp;
+
+    void
+    testStream()
+    {
+        net::io_context ioc;
+        {
+            tcp::socket s(ioc);
+            tcp_stream s1(std::move(s));
+        }
+    }
+
+    void
+    run()
+    {
+        testStream();
+        pass();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(beast,core,tcp_stream);
+
+} // beast
+} // boost