rt: Change the win32 event object to an auto-reset event

The way I read the docs, having this be a manual reset event means
that after the first time it's signalled it stays that way until reset,
and we never, ever reset it.

src/rt/sync/lock_and_signal.cpp

@@ -18,7 +18,7 @@
 lock_and_signal::lock_and_signal()
     : _holding_thread(INVALID_THREAD)
 {
-    _event = CreateEvent(NULL, TRUE, FALSE, NULL);
+    _event = CreateEvent(NULL, FALSE, FALSE, NULL);
     InitializeCriticalSection(&_cs);
 }