security: Added headers for der encoding.  Added CertificateExtension and CertificateSubjectDescription.
diff --git a/Makefile.am b/Makefile.am
index 807e8f7..3928da1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -47,6 +47,8 @@
   include/ndn-cpp/security/security-common.hpp \
   include/ndn-cpp/security/key-chain.hpp \
   include/ndn-cpp/security/security-exception.hpp \
+  include/ndn-cpp/security/certificate/certificate-extension.hpp \
+  include/ndn-cpp/security/certificate/certificate-subject-description.hpp \
   include/ndn-cpp/security/certificate/certificate.hpp \
   include/ndn-cpp/security/certificate/identity-certificate.hpp \
   include/ndn-cpp/security/certificate/public-key.hpp \
@@ -114,8 +116,16 @@
   ndn-cpp/encoding/element-listener.cpp \
   ndn-cpp/encoding/oid.cpp \
   ndn-cpp/encoding/wire-format.cpp \
+  ndn-cpp/encoding/der/der.hpp \
+  ndn-cpp/encoding/der/visitor/no-arguments-visitor.hpp \
+  ndn-cpp/encoding/der/visitor/simple-visitor.hpp \
+  ndn-cpp/encoding/der/visitor/visitor.hpp \
+  ndn-cpp/encoding/der/visitor/void-no-arguments-visitor.hpp \
+  ndn-cpp/encoding/der/visitor/void-visitor.hpp \
   ndn-cpp/security/key-chain.cpp \
   ndn-cpp/security/security-exception.cpp \
+  ndn-cpp/security/certificate/certificate-extension.cpp \
+  ndn-cpp/security/certificate/certificate-subject-description.cpp \
   ndn-cpp/security/certificate/public-key.cpp \
   ndn-cpp/security/identity/basic-identity-storage.cpp \
   ndn-cpp/security/identity/identity-manager.cpp \