The "count_" out-parameter is doubled instead of unchanged.

Static analysis says:
src\zmq.cpp(489): error V220: Suspicious sequence of types castings: memsize -> 32-bit integer -> memsize. The value being casted: '* count_'.
src\zmq.cpp(510): error V127: An overflow of the 32-bit 'nread' variable is possible inside a long cycle which utilizes a memsize-type loop counter.

I've silenced the warning on line 489 and ignored the other.
But also, it looks to me like there's a serious bug here: The
out-parameter "count_" is never set to zero before we start
incrementing it. So its final value will always be between
1 and 2 times its initial value. The fix seems obvious.

src/zmq.cpp

@@ -486,9 +486,11 @@ int zmq_recviov (void *s_, iovec *a_, size_t *count_, int flags_)
     }
     zmq::socket_base_t *s = (zmq::socket_base_t *) s_;
 
-    size_t count = (int) *count_;
+    size_t count = *count_;
     int nread = 0;
     bool recvmore = true;
+    
+    *count_ = 0;
 
     for (size_t i = 0; recvmore && i < count; ++i) {
         // Cheat! We never close any msg