connector: Check for POLLHUP on in_fd

POLLHUP needs to be checked on in_fd, which may be a pipe.
A pipe in Linux signals EOF through POLLHUP (see:
http://www.greenend.org.uk/rjk/tech/poll.html)

Without checking POLLHUP, a client could spin up indefinetely
doing ssh_event_dopoll.

Signed-off-by: Alberto Aguirre <albaguirre@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/connector.c

@@ -370,7 +370,7 @@ static int ssh_connector_fd_cb(ssh_poll_handle p,
 
     if (revents & POLLERR) {
         ssh_connector_except(connector, fd);
-    } else if((revents & POLLIN) && fd == connector->in_fd) {
+    } else if((revents & (POLLIN|POLLHUP)) && fd == connector->in_fd) {
         ssh_connector_fd_in_cb(connector);
     } else if((revents & POLLOUT) && fd == connector->out_fd) {
         ssh_connector_fd_out_cb(connector);