add required libraries

external/include/json/json.h

@@ -0,0 +1,15 @@
+// Copyright 2007-2010 Baptiste Lepilleur and The JsonCpp Authors
+// Distributed under MIT license, or public domain if desired and
+// recognized in your jurisdiction.
+// See file LICENSE for detail or copy at http://jsoncpp.sourceforge.net/LICENSE
+
+#ifndef JSON_JSON_H_INCLUDED
+#define JSON_JSON_H_INCLUDED
+
+#include "config.h"
+#include "json_features.h"
+#include "reader.h"
+#include "value.h"
+#include "writer.h"
+
+#endif // JSON_JSON_H_INCLUDED