[MEDIUM] poll: add a measurement of idle vs work time

We now measure the work and idle times in order to report the idle
time in the stats. It's expected that we'll be able to use it at
other places later.
diff --git a/src/ev_kqueue.c b/src/ev_kqueue.c
index e167984..b43533a 100644
--- a/src/ev_kqueue.c
+++ b/src/ev_kqueue.c
@@ -126,6 +126,7 @@
 	}
 
 	fd = MIN(maxfd, global.tune.maxpollevents);
+	gettimeofday(&before_poll, NULL);
 	status = kevent(kqueue_fd, // int kq
 			NULL,      // const struct kevent *changelist
 			0,         // int nchanges
@@ -133,6 +134,7 @@
 			fd,        // int nevents
 			&timeout); // const struct timespec *timeout
 	tv_update_date(delta_ms, status);
+	measure_idle();
 
 	for (count = 0; count < status; count++) {
 		fd = kev[count].ident;