split export symbols from rtm.c to each file

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2263 bbd45198-f89e-11dd-88c7-29a3b14d5316

src/clock.c

@@ -52,6 +52,7 @@ rt_tick_t rt_tick_get(void)
 	/* return the global tick */
 	return rt_tick;
 }
+RTM_EXPORT(rt_tick_get);
 
 /**
  * This function will set current tick
@@ -105,6 +106,7 @@ rt_tick_t rt_tick_from_millisecond(rt_uint32_t ms)
 	/* return the calculated tick */
 	return (RT_TICK_PER_SECOND * ms + 999) / 1000;
 }
+RTM_EXPORT(rt_tick_from_millisecond);
 
 /*@}*/