The draft ACATS test (which we developed) for the Ada 2022 feature of
user-defined literals has compile-time problems that are fixed with this
set of changes.  Two of these involve the resolution of named numbers
in the context where an implicit literal conversion can occur, and for
equality when a literal or named number is an operand. Furthermore,
the compiler can hang in some cases when a numeric literal is used
in a context where the expected type is a type derived two levels
down from a tagged type that specifies a literal aspect.

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

gcc/ada/

	* sem_res.adb
	(Resolve_Equality_Op): Add handling for equality ops with
	user-defined literal operands.
	* sem_util.ads
	(Is_User_Defined_Literal): Update spec comment to indicate
	inclusion of named number cases.
	* sem_util.adb
	(Corresponding_Primitive_Op): Rather than following the chain of
	ancestor subprograms via Alias and Overridden_Operation links, we
	check for matching profiles between primitive subprograms of the
	descendant type and the ancestor subprogram (by calling a new
	nested function Profile_Matches_Ancestor). This prevents the
	compiler from hanging due to circular linkages via those fields
	that can occur between inherited and overriding subprograms
	(which might indicate a latent bug, but one that may be rather
	delicate to resolve).
	(Profile_Matches_Ancestor): New nested subprogram to compare the
	profile of a primitive subprogram with the profile of a candidate
	ancestor subprogram.
	(Is_User_Defined_Literal): Also return True in cases where the
	node N denotes a named number (E_Name_Integer and E_Named_Real).