The front-end defines an Any_Access entity which is only used as the type
of the literal null.  Now, since AI95-0230, the RM 4.2(8/2) clause reads:
"An integer literal is of type universal_integer. A real literal is of type
universal_real. The literal null is of type universal_access." and e.g.
Find_Non_Universal_Interpretations deals with Any_Access as if it was an
universal type, so it is more consistent to rename it into Universal_Access.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* stand.ads (Any_Access): Delete.
	(Universal_Access): New entity.
	* einfo.ads: Remove obsolete reference to Any_Access.
	* gen_il-gen-gen_entities.adb: Likewise.
	* cstand.adb (Create_Standard): Do not create Any_Access and create
	Universal_Access as a full type instead.
	* errout.adb (Set_Msg_Insertion_Type_Reference): Do not deal with
	Any_Access and deal with Universal_Access instead.
	* sem_ch3.adb (Analyze_Object_Declaration): Replace Any_Access with
	Universal_Access.
	* sem_ch4.adb (Analyze_Null): Likewise.
	(Find_Non_Universal_Interpretations): Likewise.
	(Find_Equality_Types.Try_One_Interp): Likewise and avoid shadowing
	by renaming a local variable of the same name.
	* sem_res.adb (Make_Call_Into_Operato): Likewise.
	(Resolve_Equality_Op): Likewise.
	* sem_type.adb (Covers): Likewise.
	(Specific_Type): Likewise.