opt.ads (Warn_On_Suspicious_Contract): Update comment describing use.

opt.ads (Warn_On_Suspicious_Contract): Update comment describing use.

2015-02-05  Yannick Moy  <moy@adacore.com>

	* opt.ads (Warn_On_Suspicious_Contract): Update comment
	describing use.
	* sem_attr.adb (Analyze_Attribute/Attribute_Update): Warn on
	suspicious uses of 'Update.
	* sem_warn.adb, sem_warn.ads (Warn_On_Suspicious_Update): New
	function issues warning on suspicious uses of 'Update.
	* g-rannum.adb, g-rannum.ads, s-rannum.adb, s-rannum.ads: Mark
	package spec and body as SPARK_Mode Off.

From-SVN: r220444