Obsolete ECANTROUTE errror code removed

This error code was used only by new-style ROUTER socket
which is not a part of the codebase.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

include/zmq.h

@@ -112,7 +112,6 @@ ZMQ_EXPORT void zmq_version (int *major, int *minor, int *patch);
 #define ENOCOMPATPROTO (ZMQ_HAUSNUMERO + 52)
 #define ETERM (ZMQ_HAUSNUMERO + 53)
 #define EMTHREAD (ZMQ_HAUSNUMERO + 54)
-#define ECANTROUTE (ZMQ_HAUSNUMERO + 55)
 
 /*  This function retrieves the errno as it is known to 0MQ library. The goal */
 /*  of this function is to make the code 100% portable, including where 0MQ   */