* rtsfind.ads Remove the entries for Ada.Synchronous_Task_Control
and Suspension_Object from tables RE_Id, RE_Unit_Table and RTU_Id.
* sem_util.adb (Is_Descendant_Of_Suspension_Object): Update
the comment on usage. Use routine Is_Suspension_Object to detect
whether a type matches Suspension_Object.
(Is_Suspension_Object): New routine.
* snames.ads-tmpl: Add predefined names for Suspension_Object
and Synchronous_Task_Control.