struct rt_thread 的 stack_size 改回 rt_uint16_t 类

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@998 bbd45198-f89e-11dd-88c7-29a3b14d5316

include/rtdef.h

@@ -323,7 +323,7 @@ struct rt_thread
 	void*		entry;									/* entry 									*/
 	void*       parameter;								/* parameter 								*/
 	void*       stack_addr;								/* stack address 							*/
-	rt_uint32_t stack_size;								/* stack size 								*/
+	rt_uint16_t stack_size;								/* stack size 								*/
 
 	/* error code */
 	rt_err_t    error;									/* error code 								*/