[Ada] Bad handling of 'Valid_Scalars and arrays

[Ada] Bad handling of 'Valid_Scalars and arrays

gcc/ada/

	* exp_attr.adb (Build_Array_VS_Func, Build_Record_VS_Func,
	Expand_N_Attribute_Reference): Use Get_Fullest_View instead of
	Validated_View.
	(Build_Record_VS_Func): Adjust to keep using Validated_View.
	(Expand_N_Attribute_Reference) [Valid]: Use
	Small_Integer_Type_For to allow for more compile time
	evaluations.
	* sem_util.adb (Cannot_Raise_Constraint_Error): Add more precise
	support for N_Indexed_Component and fix support for
	N_Selected_Component which wasn't completely safe.
	(List_Cannot_Raise_CE): New.
	* libgnat/i-cobol.adb (Valid_Packed): Simplify test to address
	new GNAT warning.