ada: Fix spurious visibility error on parent's component in instance

ada: Fix spurious visibility error on parent's component in instance

This occurs for an aggregate of a derived tagged type in the body of the
instance, because the full view of the parent type, which was visible in
the generic construct (otherwise the aggregate would have been illegal),
is not restored in the body of the instance.

Copy_Generic_Node already contains code to restore the full view in this
case, but it works only if the derived tagged type is itself global to
the generic construct, and not if the derived tagged type is local but
the parent type global, as is the case here.

gcc/ada/

	* gen_il-fields.ads (Aggregate_Bounds): Rename to
	Aggregate_Bounds_Or_Ancestor_Type.
	* gen_il-gen-gen_nodes.adb (Aggregate_Bounds): Likewise.
	* sem_aggr.adb (Resolve_Record_Aggregate): Remove obsolete bypass.
	* sem_ch12.adb (Check_Generic_Actuals): Add decoration.
	(Copy_Generic_Node): For an extension aggregate, restore only the
	full view, if any.  For a full aggregate, restore the full view as
	well as that of its Ancestor_Type, if any, and up to the root type.
	(Save_References_In_Aggregate): For a full aggregate of a local
	derived tagged type with a global ancestor, set Ancestor_Type to
	this ancestor.  For a full aggregate of a global derived tagged
	type, set Ancestor_Type to the parent type.
	* sinfo-utils.ads (Aggregate_Bounds): New function renaming.
	(Ancestor_Type): Likewise.
	(Set_Aggregate_Bounds): New procedure renaming.
	(Set_Ancestor_Type): Likewise.
	* sinfo.ads (Ancestor_Type): Document new field.