Problem: nodrop code is ugly

It's bad practice to start by testing all exceptional conditions
and then dropping through to the 'normal' condition. Apart from
being inefficient, it's deceptive to the user. Conditional code
should always try to show the natural expectation of the code,
with exceptional cases coming last.

Solution: clean up this code.

src/xpub.cpp

@@ -132,25 +132,20 @@ int zmq::xpub_t::xsend (msg_t *msg_)
         subscriptions.match ((unsigned char*) msg_->data (), msg_->size (),
             mark_as_matching, this);
 
-    if (lossy == false && !dist.check_hwm ()) {
-        errno = EAGAIN;
-        return -1;
-    }
-
-    //  Send the message to all the pipes that were marked as matching
-    //  in the previous step.
-    int rc = dist.send_to_matching (msg_);
-    if (rc != 0)
-        return rc;
-
-    //  If we are at the end of multi-part message we can mark all the pipes
-    //  as non-matching.
+    int rc = -1;            //  Assume we fail
+    if (lossy || dist.check_hwm ()) {
+        if (dist.send_to_matching (msg_) == 0) {
+            //  If we are at the end of multi-part message we can mark 
+            //  all the pipes as non-matching.
             if (!msg_more)
                 dist.unmatch ();
-
             more = msg_more;
-
-    return 0;
+            rc = 0;         //  Yay, sent successfully
+        }
+    }
+    else
+        errno = EAGAIN;
+    return rc;
 }
 
 bool zmq::xpub_t::xhas_out ()