Auto merge of #442 - asomers:kevent, r=posborne

impl Send for KEvent

carllerche/mio needs KEvent to be Send-able.  It's safe to send because udata is always treated as a uintptr_t.  The only ways to use udata that wouldn't be Send-able would also be unsafe because they would require casting udata to a pointer.  So I think it's safe to add the Send trait to KEvent.

src/sys/event.rs

@@ -191,6 +191,15 @@ pub fn kqueue() -> Result<RawFd> {
     Errno::result(res)
 }
 
+
+/*
+ * KEvent can't derive Send because on some operating systems, udata is defined
+ * as a void*.  However, KEvent's public API always treats udata as a uintptr_t,
+ * which is safe to Send.
+ */
+unsafe impl Send for KEvent {
+}
+
 impl KEvent {
     pub fn new(ident: uintptr_t, filter: EventFilter, flags: EventFlag,
                fflags:FilterFlag, data: intptr_t, udata: uintptr_t) -> KEvent {