Use kqueue on Darwin as well

Since poll() is implemented in terms of kqueue() there,
it doesn't seem like this could have improved anything.

Besides man 3 ev, libevent code, and [1],
I haven't managed to find much relevant information.

[1] https://daniel.haxx.se/blog/2016/10/11/poll-on-mac-10-12-is-broken/

liberty.c

@@ -1749,10 +1749,9 @@ poller_run (struct poller *self)
 	self->revents_len = 0;
 }
 
-#elif defined (BSD)
+// Sort of similar to the epoll version.  Let's hope Darwin isn't broken,
-
+// that'd mean reimplementing this in terms of select() just because of Crapple.
-// Mac OS X's kqueue is fatally broken, or so I've been told; leaving it out.
+#elif defined (BSD) || defined (__APPLE__)
-// Otherwise this is sort of similar to the epoll version.
 
 #include <sys/types.h>
 #include <sys/event.h>