util: switch to boost::asio::basic_waitable_timer

Change-Id: I2724befc86482adf84f59063e65509a116bb1b46
Refs: #4431
diff --git a/src/common-pch.hpp b/src/common-pch.hpp
index 58c4513..12be185 100644
--- a/src/common-pch.hpp
+++ b/src/common-pch.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -40,7 +40,6 @@
 // Boost headers to precompile
 #include <boost/algorithm/string.hpp>
 #include <boost/chrono.hpp>
-#include <boost/date_time/posix_time/posix_time.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/iostreams/categories.hpp>
 #include <boost/iostreams/stream.hpp>