Fix compilation using MSVC 2008: stdint.h is not present in this compiler

This patch fixes the two headers added recently to include our own "stdint.hpp" instead of system <stdint.h> because the latter is not available in Visual Studio versions prior to 2010.

src/i_encoder.hpp

@@ -21,7 +21,7 @@
 #ifndef __ZMQ_I_ENCODER_HPP_INCLUDED__
 #define __ZMQ_I_ENCODER_HPP_INCLUDED__
 
-#include <stdint.h>
+#include "stdint.hpp"
 
 namespace zmq
 {