avoid blocking the notify thread, fixup event on win32

The prior io thread had a couple of issues; consuming from the
inotify fd is actually a blocking operation, so we need to add
a check to our loop condition.

Fixup how we interpret the result of a wait on a win32 event,
so that we don't falsely believe that is has been satisfied
in the timeout case (doh!)

root.c

@@ -1733,6 +1733,9 @@ static void notify_thread(w_root_t *root)
         if (w_ht_size(root->pending_uniq) >= WATCHMAN_BATCH_LIMIT) {
           break;
         }
+        if (!wait_for_notify(root, 0)) {
+          break;
+        }
       }
       w_event_set(root->have_pending_evt);
     }
@@ -1782,7 +1785,9 @@ static void io_thread(w_root_t *root)
 
     // Wait for the notify thread to give us pending items, or for
     // the settle period to expire
+    w_log(W_LOG_DBG, "poll_events timeout=%dms\n", timeoutms);
     w_poll_events(&pevt, 1, timeoutms);
+    w_log(W_LOG_DBG, " ... wake up\n");
     if (!w_event_test_and_clear(root->have_pending_evt)) {
       // No new pending items were given to us, so consider that
       // we may not be settled.

stream_win.c

@@ -506,7 +506,7 @@ void w_event_destroy(w_evt_t evt) {
 }
 
 bool w_event_test_and_clear(w_evt_t evt) {
-  bool was_set = WaitForSingleObject(evt, 0);
+  bool was_set = WaitForSingleObject(evt, 0) == WAIT_OBJECT_0;
   ResetEvent(evt);
   return was_set;
 }