[Ada] Transform_Function_Array issues

gcc/ada/

	* exp_ch6.adb (Build_Procedure_Body_Form): Adjust, the
	declaration of the procedure form is now insert before the
	original function body rather than after.
	(Expand_N_Subprogram_Declaration): Deal with private types whose
	full views are arrays.
	* exp_unst.adb (Unnest_Subprogram): Deal with private types.
	(Needs_Fat_Pointer): Code cleanup.
	* freeze.adb (Freeze_Subprogram): Ditto.
	* exp_util.adb (Build_Procedure_Form): Insert the procedure form
	decl before and not after.
	* sem_ch6.adb (Analyze_Subprogram_Body_Helper): Build missing
	spec when needed for Transform_Function_Array.
	* sem_util.adb (Get_Fullest_View): Deal with null entity.