Migrate remaining c++03 examples to c++11.

example/cpp11/tutorial/timer2/timer.cpp

@@ -0,0 +1,29 @@
+//
+// timer.cpp
+// ~~~~~~~~~
+//
+// Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <iostream>
+#include <boost/asio.hpp>
+
+void print(const boost::system::error_code& /*e*/)
+{
+  std::cout << "Hello, world!" << std::endl;
+}
+
+int main()
+{
+  boost::asio::io_context io;
+
+  boost::asio::steady_timer t(io, boost::asio::chrono::seconds(5));
+  t.async_wait(&print);
+
+  io.run();
+
+  return 0;
+}