lib-xref.adb (Generate_Reference): Handle properly a reference to an entry formal...

	* lib-xref.adb (Generate_Reference): Handle properly a reference to an
	entry formal, when an accept statement has a pragma Unreferenced for it.

	* sem_ch9.adb (Analyze_Accept_Statement): Reset the Is_Referenced flag
	and the Has_Pragma_Unreferenced flag for each formal before analyzing
	the body, to ensure that warnings are properly emitted for each accept
	statement of a given task entry.

From-SVN: r91888