build: suppress CryptoPP warnings

Change-Id: I52e93fb18c42cf72d73c4477dc4a8093a5221215
diff --git a/src/util/crypto.cpp b/src/util/crypto.cpp
index 3aa114a..1621005 100644
--- a/src/util/crypto.cpp
+++ b/src/util/crypto.cpp
@@ -6,9 +6,7 @@
 #include "../common.hpp"
 
 #include "crypto.hpp"
-#include <cryptopp/sha.h>
-#include <cryptopp/filters.h>
-#include <cryptopp/files.h>
+#include "../security/cryptopp.hpp"
 
 namespace ndn {