Update linux host to handle SIGHUP. use it to reload config.

remoting/host/sighup_listener_mac.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-//
-// This file implements a signal handler that is used to safely handle SIGHUP
-// and trigger the specified callback. It is currently used on Mac in order to
-// reload the me2me host configuration, but would need minimal changes on Linux.
-
-#ifndef REMOTING_HOST_SIGHUP_LISTENER_MAC_H_
-#define REMOTING_HOST_SIGHUP_LISTENER_MAC_H_
-
-#include "base/callback_forward.h"
-
-namespace remoting {
-
-// Register for SIGHUP notifications on the current thread, which must have
-// an associated MessageLoopForIO.
-bool RegisterHupSignalHandler(const base::Closure& callback);
-
-}  // namespace remoting
-
-#endif  // REMOTING_HOST_SIGHUP_LISTENER_MAC_H_