sem_util.adb (Check_Result_And_Post_State): Do not issue a warning about missing reference to an outcome if...

2017-09-11  Yannick Moy  <moy@adacore.com>

	* sem_util.adb (Check_Result_And_Post_State):
	Do not issue a warning about missing reference to an outcome if
	the subprogram is ghost and has no outputs.
	* lib-xref-spark_specific.adb, sem_aggr.adb, sem_aux.ads: Minor
	reformatting.

From-SVN: r251960