Problem: remaining uses of "identity"

Solution: replaced by "routing id"

src/pipe.hpp

@@ -226,10 +226,10 @@ namespace zmq
         //  asks us to.
         bool delay;
 
-        //  Identity of the writer. Used uniquely by the reader side.
+        //  Routing id of the writer. Used uniquely by the reader side.
         blob_t router_socket_routing_id;
 
-        //  Identity of the writer. Used uniquely by the reader side.
+        //  Routing id of the writer. Used uniquely by the reader side.
         int server_socket_routing_id;
 
         //  Pipe's credential.

tests/test_spec_req.cpp

@@ -167,7 +167,7 @@ void test_req_message_format (void *ctx)
     zmq_msg_t msg;
     zmq_msg_init (&msg);
 
-    // Receive peer identity
+    // Receive peer routing id
     rc = zmq_msg_recv (&msg, router, 0);
     assert (rc != -1);
     assert (zmq_msg_size (&msg) > 0);