util: Support MustBeFresh processing in InMemoryStorage

Change-Id: I8e8e647d7673e4e0fe8dd1c5025fbc8e5e524c70
Refs: #3274
diff --git a/src/util/in-memory-storage-persistent.hpp b/src/util/in-memory-storage-persistent.hpp
index cd9faa3..3cd12ef 100644
--- a/src/util/in-memory-storage-persistent.hpp
+++ b/src/util/in-memory-storage-persistent.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -33,9 +33,11 @@
 class InMemoryStoragePersistent : public InMemoryStorage
 {
 public:
-  explicit
   InMemoryStoragePersistent();
 
+  explicit
+  InMemoryStoragePersistent(boost::asio::io_service& ioService);
+
   virtual
   ~InMemoryStoragePersistent();