security: Add doxygen comments

Change-Id: Ieafe4d13513e626d84ef9e621694f69844785018
diff --git a/src/security/validator.hpp b/src/security/validator.hpp
index 5a1062d..7a75f70 100644
--- a/src/security/validator.hpp
+++ b/src/security/validator.hpp
@@ -6,8 +6,8 @@
  * See COPYING for copyright and distribution information.
  */
 
-#ifndef NDN_VALIDATOR_HPP
-#define NDN_VALIDATOR_HPP
+#ifndef NDN_SECURITY_VALIDATOR_HPP
+#define NDN_SECURITY_VALIDATOR_HPP
 
 #include "../common.hpp"
 
@@ -152,6 +152,6 @@
   shared_ptr<Face> m_face;
 };
 
-}
+} // namespace ndn
 
-#endif
+#endif //NDN_SECURITY_VALIDATOR_HPP