[Ada] Refine types of variables with call to Scope as their initial values

gcc/ada/

	* exp_ch4.adb (User_Defined_Primitive_Equality_Op): Refine type
	of a local variable.
	* exp_dbug.adb (Scope_Contains): Refine all types from Node_Id
	to Entity_Id; rename parameters to match those of the
	Scope_Within routine (which is similar but not the same); also,
	simplify an OR ELSE into a membership test.