Cleanup iostream includes

Change-Id: I16dd945998463975b140c7a010d64a112f95d8ba
diff --git a/src/security/transform/stream-source.cpp b/src/security/transform/stream-source.cpp
index 539506e..33b26ae 100644
--- a/src/security/transform/stream-source.cpp
+++ b/src/security/transform/stream-source.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2016 Regents of the University of California.
+/*
+ * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -20,6 +20,8 @@
  */
 
 #include "stream-source.hpp"
+
+#include <istream>
 #include <vector>
 
 namespace ndn {