2017-09-08  Yannick Moy  <moy@adacore.com>

	* sem_aux.adb, sem_aux.ads (Get_Called_Entity): New function to
	return the entity associated with the call.
	* sem_util.adb, sem_util.ads (Check_Function_Writable_Actuals):
	Replace the internal Get_Function_Id with the new
	Sem_Aux.Get_Called_Entity.
	(Iterate_Call_Parameters): New
	procedure to iterate on formals and actuals at the same time.
	* sem_ch12.adb (Analyze_Subprogram_Instantiation):
	Set SPARK_Mode from spec when set, for analysis
	of instance. Restore after analysis of instance.
	(Instantiate_Subprogram_Body): Set SPARK_Mode from body when
	set, for analysis of body instance. Restored automatically at
	the end of the subprogram.
	* gnat1drv.adb (Adjust_Global_Switches): Set
	Check_Validity_Of_Parameters to False in GNATprove mode.
	* opt.ads (Check_Validity_Of_Parameters): Document switch to
	set option.

From-SVN: r251900