Xext: lift sleeputil.c to xorg-xserver-7.1/1.1 state

nx-X11/programs/Xserver/Xext/sleepuntil.c

@@ -78,7 +78,7 @@ static void	    SertafiedWakeupHandler(
     void * /* LastSelectMask */
 );
 
-int
+_X_EXPORT int
 ClientSleepUntil (client, revive, notifyFunc, closure)
     ClientPtr	client;
     TimeStamp	*revive;