[Ada] Refine logic to set Needs_Activation_Record on subprogram types

[Ada] Refine logic to set Needs_Activation_Record on subprogram types

2018-05-30  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_ch3.adb (Access_Subprogram_Declaration): The flag
	Needs_Activation_Record is only needed on a subprogram type, not on a
	pointer to such.
	* sem_res.adb (Resolve_Selected_Component): If the context type and the
	component type are anonymous access to subprograms, use the component
	type to obtain the proper value of Needs_Activation_Record flag for the
	expression.

From-SVN: r260932