Revert earlier change that removes warnings, but breaks Windows compilation.

extra/libevent/devpoll.c

@@ -185,9 +185,7 @@ devpoll_init(struct event_base *base)
 }
 
 static int
-devpoll_recalc(struct event_base *base __attribute__((unused)),
-               void *arg __attribute__((unused)),
-               int max)
+devpoll_recalc(struct event_base *base, void *arg, int max)
 {
 	struct devpollop *devpollop = arg;
 

extra/libevent/evbuffer.c

@@ -75,8 +75,7 @@ bufferevent_add(struct event *ev, int timeout)
  */
 
 void
-bufferevent_read_pressure_cb(struct evbuffer *buf,
-                             size_t old __attribute__((unused)), size_t now,
+bufferevent_read_pressure_cb(struct evbuffer *buf, size_t old, size_t now,
     void *arg) {
 	struct bufferevent *bufev = arg;
 	/*