[Ada] ACATS 4.1L - B452002 - Wrong universal access "=" rules

[Ada] ACATS 4.1L - B452002 - Wrong universal access "=" rules

2020-06-18  Arnaud Charlet  <charlet@adacore.com>

gcc/ada/

	* sem_ch4.adb (Find_Equality_Types.Check_Access_Object_Types):
	New function, used to implement RM 4.5.2 (9.6/2).
	(Find_Equality_Types.Check_Compatible_Profiles): New function,
	used to implement RM 4.5.2(9.7/2).
	(Find_Equality_Types.Reference_Anonymous_Access_Type): New
	function.
	(Find_Equality_Types.Try_One_Interp): Fix handling of anonymous
	access types which was accepting both too much and too little.
	Remove accumulated special and incomplete cases for
	instantiations, replaced by Has_Compatible_Type.
	(Analyze_Overloaded_Selected_Component): Use
	Is_Anonymous_Access_Type instead of Ekind_In.
	* sem_res.adb: Code cleanup and bug fix: use
	Is_Anonymous_Access_Type instead of Ekind_In.  Relax checking of
	anonymous access parameter when universal_access "=" is
	involved.
	* sem_type.adb: Likewise.
	(Find_Unique_Type): Move code from here...
	(Specific_Type): ...to here. Also add missing handling of access
	to class wide types.
	* einfo.ads, einfo.adb (Is_Access_Object_Type): New.