resolve #1325 Alignment issue with zmq_msg_t on SPARC CPU

should be backported probably

include/zmq.h

@@ -195,7 +195,10 @@ ZMQ_EXPORT int zmq_ctx_destroy (void *context);
 /*  0MQ message definition.                                                   */
 /******************************************************************************/
 
-typedef struct zmq_msg_t {unsigned char _ [64];} zmq_msg_t;
+/* union here ensures correct alignment on architectures that require it, e.g.
+ * SPARC
+ */
+typedef union zmq_msg_t {unsigned char _ [64]; void *p; } zmq_msg_t;
 
 typedef void (zmq_free_fn) (void *data, void *hint);