Tidy up warnings and deprecated usage:

fix #1290

* BOOST_ASIO_NO_DEPRECATED=1 is now set
* Fix various warnings from the Boost regression test matrix
* Fix a bug in advanced servers when checking for a timeout

example/advanced/server-flex/advanced_server_flex.cpp

@@ -809,7 +809,7 @@ public:
             return fail(ec, "timer");
 
         // Check if this has been upgraded to Websocket
-        if(timer_.expires_at() == (std::chrono::steady_clock::time_point::min)())
+        if(timer_.expiry() == (std::chrono::steady_clock::time_point::min)())
             return;
 
         // Verify that the timer really expired since the deadline may have moved.