Windows build fixed

Compilation of ip.cpp have failed because EPROTONOSUPPORT
was undefined. Including zmq.h should help as the error
code is defined there.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/ip.cpp

@@ -23,6 +23,8 @@
 #include <stdlib.h>
 #include <string>
 
+#include "../include/zmq.h"
+
 #include "ip.hpp"
 #include "platform.hpp"
 #include "err.hpp"