build: Experimental support to build using precompiled headers

This type of build needs to be explicitly enabled using --with-pch
configure option.

Change-Id: I02dc304187d54c3cf40f1d51b1b11b21f868e225
diff --git a/src/security/identity-certificate.hpp b/src/security/identity-certificate.hpp
index 65b07af..fa31966 100644
--- a/src/security/identity-certificate.hpp
+++ b/src/security/identity-certificate.hpp
@@ -9,6 +9,7 @@
 #ifndef NDN_IDENTITY_CERTIFICATE_HPP
 #define NDN_IDENTITY_CERTIFICATE_HPP
 
+#include "../common.hpp"
 #include "certificate.hpp"
 
 namespace ndn {