Problem: tabs instead of spaces used for indentation

Solution: correct it to spaces

src/socket_poller.cpp

@@ -393,10 +393,10 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *event_, long time
 
 #if defined ZMQ_POLL_BASED_ON_POLL
     if (unlikely (poll_size == 0)) {
-	// We'll report an error (timed out) as if the list was non-empty and
-	// no event occured within the specified timeout. Otherwise the caller
-	// needs to check the return value AND the event to avoid using the
-	// nullified event data.
+        // We'll report an error (timed out) as if the list was non-empty and
+        // no event occured within the specified timeout. Otherwise the caller
+        // needs to check the return value AND the event to avoid using the
+        // nullified event data.
         errno = ETIMEDOUT;
         if (timeout_ == 0)
             return -1;