ada: Deep delta aggregates

ada: Deep delta aggregates

Add support for "deep" delta aggregates, a GNAT-defined language extension
conditionally enabled via the -gnatX0 switch. In a deep delta aggregate, a
delta choice may specify a subcomponent (as opposed to just a component).

gcc/ada/

	* par.adb: Add new Boolean variable Inside_Delta_Aggregate.
	* par-ch4.adb (P_Simple_Expression): Add support for a deep delta
	aggregate choice. We turn a sequence of selectors into a peculiar
	tree. We build a component (Indexed or Selected) whose prefix is
	another such component, etc. The leftmost prefix at the bottom of
	the tree has a "name" which is the first selector, without any
	further prefix. For something like "with delta (1)(2) => 3" where
	the type of the aggregate is an array of arrays of integers, we'll
	build an N_Indexed_Component whose prefix is an integer literal 1.
	This is consistent with the trees built for "regular"
	(Ada-defined) delta aggregates.
	* sem_aggr.adb (Is_Deep_Choice, Is_Root_Prefix_Of_Deep_Choice):
	New queries.
	(Resolve_Deep_Delta_Assoc): new procedure.
	(Resolve_Delta_Array_Aggregate): call Resolve_Deep_Delta_Assoc in
	deep case.
	(Resolve_Delta_Record_Aggregate): call Resolve_Deep_Delta_Assoc in
	deep case.
	(Get_Component_Type): new function replaces old Get_Component
	function.
	* sem_aggr.ads (Is_Deep_Choice, Is_Root_Prefix_Of_Deep_Choice):
	New queries.
	* exp_aggr.adb (Expand_Delta_Array_Aggregate): add nested function
	Make_Array_Delta_Assignment_LHS; call it instead of
	Make_Indexed_Component.
	(Expand_Delta_Record_Aggregate): add nested function
	Make_Record_Delta_Assignment_LHS; call it instead of
	Make_Selected_Component.
	* exp_spark.adb (Expand_SPARK_Delta_Or_Update): Insert range
	checks for indexes in deep delta aggregates.