Update boost to 1.71 and add asio

boost/asio/wait_traits.hpp

@@ -0,0 +1,58 @@
+//
+// wait_traits.hpp
+// ~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2019 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)
+//
+
+#ifndef BOOST_ASIO_WAIT_TRAITS_HPP
+#define BOOST_ASIO_WAIT_TRAITS_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/push_options.hpp>
+
+namespace boost {
+namespace asio {
+
+/// Wait traits suitable for use with the basic_waitable_timer class template.
+template <typename Clock>
+struct wait_traits
+{
+  /// Convert a clock duration into a duration used for waiting.
+  /**
+   * @returns @c d.
+   */
+  static typename Clock::duration to_wait_duration(
+      const typename Clock::duration& d)
+  {
+    return d;
+  }
+
+  /// Convert a clock duration into a duration used for waiting.
+  /**
+   * @returns @c d.
+   */
+  static typename Clock::duration to_wait_duration(
+      const typename Clock::time_point& t)
+  {
+    typename Clock::time_point now = Clock::now();
+    if (now + (Clock::duration::max)() < t)
+      return (Clock::duration::max)();
+    if (now + (Clock::duration::min)() > t)
+      return (Clock::duration::min)();
+    return t - now;
+  }
+};
+
+} // namespace asio
+} // namespace boost
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#endif // BOOST_ASIO_WAIT_TRAITS_HPP