[Ada] Expand controlling functions wrappers in GNATprove mode

[Ada] Expand controlling functions wrappers in GNATprove mode

gcc/ada/

	* exp_ch3.ads (Make_Controlling_Function_Wrappers): Move
	declaration from body to spec, so it can be called by
	SPARK-specific expansion.
	* exp_ch3.adb (Make_Controlling_Function_Wrappers): Likewise.
	* exp_spark.adb (SPARK_Freeze_Type): Enable expansion of
	wrappers for function with controlling result types.