[Ada] Incremental patch for restriction No_Dynamic_Accessibility_Checks

[Ada] Incremental patch for restriction No_Dynamic_Accessibility_Checks

gcc/ada/

	* sem_util.ads (Type_Access_Level): Add new optional parameter
	Assoc_Ent.
	* sem_util.adb (Accessibility_Level): Treat access discriminants
	the same as components when the restriction
	No_Dynamic_Accessibility_Checks is enabled.
	(Deepest_Type_Access_Level): Remove exception for
	Debug_Flag_Underscore_B when returning the result of
	Type_Access_Level in the case where
	No_Dynamic_Accessibility_Checks is active.
	(Function_Call_Or_Allocator_Level): Correctly calculate the
	level of Expr based on its containing subprogram instead of
	using Current_Subprogram.
	* sem_res.adb (Valid_Conversion): Add actual for new parameter
	Assoc_Ent in call to Type_Access_Level, and add test of
	No_Dynamic_Accessibility_Checks_Enabled to ensure that static
	accessibility checks are performed for all anonymous access type
	conversions.