security: change enum to enum class in security-common.hpp

Change-Id: I5565c845cd57f3457c8120b11399a105fa83418d
Refs: #3083
diff --git a/src/security/sec-tpm.hpp b/src/security/sec-tpm.hpp
index 6c27077..1ade1d6 100644
--- a/src/security/sec-tpm.hpp
+++ b/src/security/sec-tpm.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 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).
  *
@@ -194,7 +194,7 @@
    * @brief Check if a particular key exists.
    *
    * @param keyName The name of the key.
-   * @param keyClass The class of the key, e.g. KEY_CLASS_PUBLIC, KEY_CLASS_PRIVATE.
+   * @param keyClass The class of the key, e.g. KeyClass::PUBLIC, KeyClass::PRIVATE.
    * @return True if the key exists, otherwise false.
    */
   virtual bool