initial cleanup function of thread to zero.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1070 bbd45198-f89e-11dd-88c7-29a3b14d5316

src/thread.c

@@ -74,7 +74,8 @@ static rt_err_t _rt_thread_init(struct rt_thread* thread,
 	thread->error = RT_EOK;
 	thread->stat  = RT_THREAD_INIT;
 
-	/* init user data */
+	/* initialize cleanup function and user data */
+	thread->cleanup = 0;
 	thread->user_data = 0;
 
 	/* init thread timer */