Remove unused variable (found with new clang warnings.)
diff --git a/src/aio/poller_epoll.inc b/src/aio/poller_epoll.inc
index 3b566f1..e8f19c5 100644
--- a/src/aio/poller_epoll.inc
+++ b/src/aio/poller_epoll.inc
@@ -61,7 +61,6 @@
 void nn_poller_add (struct nn_poller *self, int fd,
     struct nn_poller_hndl *hndl)
 {
-    int rc;
     struct epoll_event ev;
 
     /*  Initialise the handle and add the file descriptor to the pollset. */