Change the thread interface in runtime/platform and use it starting all threads

runtime/bin/eventhandler_macos.h

Index: runtime/bin/eventhandler_macos.h
diff --git a/runtime/bin/eventhandler_macos.h b/runtime/bin/eventhandler_macos.h
index 902aa5e0dc6e097039bd159d82b87cf9c8dabe07..1bece26e17d555e462897ee81e7dc13d9b154e3c 100644
--- a/runtime/bin/eventhandler_macos.h
+++ b/runtime/bin/eventhandler_macos.h
@@ -96,7 +96,7 @@ class EventHandlerImplementation {
   struct pollfd* GetPollFds(intptr_t* size);
   void HandleEvents(struct pollfd* pollfds, int pollfds_size, int result_size);
   void HandleTimeout();
-  static void* Poll(void* args);
+  static void Poll(uword args);
   void WakeupHandler(intptr_t id, Dart_Port dart_port, int64_t data);
   void HandleInterruptFd();
   void SetPort(intptr_t fd, Dart_Port dart_port, intptr_t mask);