add EPOLLEXCLUSIVE epoll flag from linux v4.5

new flag for exclusive wakeup mode when an event source fd is attached
to multiple epoll fds but they should not all receive the events.
new in linux commit df0108c5da561c66c333bb46bfe3c1fc65905898

include/sys/epoll.h

@@ -28,6 +28,7 @@ enum EPOLL_EVENTS { __EPOLL_DUMMY };
 #define EPOLLERR 0x008
 #define EPOLLHUP 0x010
 #define EPOLLRDHUP 0x2000
+#define EPOLLEXCLUSIVE (1U<<28)
 #define EPOLLWAKEUP (1U<<29)
 #define EPOLLONESHOT (1U<<30)
 #define EPOLLET (1U<<31)