build: compile websocketpp in C++11

Change-Id: Iad6a34f2b081030c4806ecc2b8f732206bd80d7a
Refs: #1930, #2082
diff --git a/daemon/face/websocket-channel.hpp b/daemon/face/websocket-channel.hpp
index bd5604b..f7c6ae2 100644
--- a/daemon/face/websocket-channel.hpp
+++ b/daemon/face/websocket-channel.hpp
@@ -128,7 +128,8 @@
    */
   FaceCreatedCallback m_onFaceCreatedCallback;
 
-  typedef std::map< websocketpp::connection_hdl, shared_ptr<WebSocketFace> > ChannelFaceMap;
+  typedef std::map< websocketpp::connection_hdl, shared_ptr<WebSocketFace>,
+                    std::owner_less<websocketpp::connection_hdl> > ChannelFaceMap;
   ChannelFaceMap m_channelFaces;
 
   /**