fsmonitor/darwin: mark unused parameters in system callback

We pass fsevent_callback() to the system FSEventStreamCreate() function
as a callback. So we must match the expected function signature, even
though we don't care about all of the parameters. Mark the unused ones
to satisfy -Wunused-parameter.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/fsmonitor/fsm-listen-darwin.c

@@ -191,12 +191,12 @@ static void my_add_path(struct fsmonitor_batch *batch, const char *path)
 }
 
 
-static void fsevent_callback(ConstFSEventStreamRef streamRef,
+static void fsevent_callback(ConstFSEventStreamRef streamRef UNUSED,
 			     void *ctx,
 			     size_t num_of_events,
 			     void *event_paths,
 			     const FSEventStreamEventFlags event_flags[],
-			     const FSEventStreamEventId event_ids[])
+			     const FSEventStreamEventId event_ids[] UNUSED)
 {
 	struct fsmonitor_daemon_state *state = ctx;
 	struct fsm_listen_data *data = state->listen_data;