sys/socket.h: add new SO_BUSY_POLL socket option

low latency busy poll sockets are new in linux v3.11

include/sys/socket.h

@@ -199,6 +199,7 @@ struct linger
 #define SO_NOFCS                43
 #define SO_LOCK_FILTER          44
 #define SO_SELECT_ERR_QUEUE     45
+#define SO_BUSY_POLL            46
 
 #ifndef SOL_SOCKET
 #define SOL_SOCKET      1