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/certificate.hpp b/src/security/certificate.hpp
index 9871733..260638a 100644
--- a/src/security/certificate.hpp
+++ b/src/security/certificate.hpp
@@ -9,8 +9,8 @@
 #ifndef NDN_CERTIFICATE_HPP
 #define NDN_CERTIFICATE_HPP
 
-#include "../data.hpp"
 #include "../common.hpp"
+#include "../data.hpp"
 
 #include "certificate-subject-description.hpp"
 #include "certificate-extension.hpp"