[Ada] AI12-0282: shared variable control aspects on formal types

[Ada] AI12-0282: shared variable control aspects on formal types

2019-12-18  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* par-ch12.adb (P_Formal_Derived_Type_Definition): In Ada_2020
	the keyword WITH can indicate the start of aspect specifications
	and not a private type extension.
	* sem_ch12.adb (Analyze_Formal_Type): Indicate that it is a
	first subtype.
	(Instantiate_Type): New procedure
	Check_Shared_Variable_Control_Aspects to verify matching rules
	between formal and actual types. Note that an array type with
	aspect Atomic_Components is considered compatible with an array
	type whose component type is Atomic, even though the array types
	do not carry the same aspect.
	* sem_ch13.adb (Analyze_One_Aspect): Allow shared variable
	control aspects to appear on formal types.
	(Rep_Item_Too_Early): Exclude aspects on formal types.
	* sem_prag.adb (Mark_Type): Handle properly pragmas that come
	from aspects on formal types.
	(Analyze_Pragma, case Atomic_Components): Handle formal types.

From-SVN: r279512