sem_ch5.adb, [...]: Update handling of assigned value/unreferenced warnings

sem_ch5.adb, [...]: Update handling of assigned value/unreferenced warnings

2007-12-06  Robert Dewar  <dewar@adacore.com>

	* sem_ch5.adb, s-taskin.adb, a-ciorma.adb, a-coorma.adb, a-cohama.adb,
	a-cihama.adb, g-awk.adb,
	s-inmaop-posix.adb: Update handling of assigned value/unreferenced
	warnings

	* exp_smem.adb: Update handling of assigned value/unreferenced warnings

	* sem.adb: Update handling of assigned value/unreferenced warnings

	* a-exexpr-gcc.adb: Add a pragma warnings off for boolean return

	* lib-xref.ads: Improve documentation for k xref type

	* lib-xref.adb:
	Update handling of assigned value/unreferenced warnings
	(Generate_Reference): Warning for reference to entity for which a
	pragma Unreferenced has been given should be unconditional.
	If the entity is a discriminal, mark the original
	discriminant as referenced.

	* sem_warn.ads, sem_warn.adb
	(Check_One_Unit): Test Renamed_In_Spec to control giving warning for
	no entities referenced in package
	(Check_One_Unit): Don't give message about no entities referenced in
	a package if a pragma Unreferenced has appeared.
	Handle new warning flag -gnatw.a/-gnatw.A
	Update handling of assigned value/unreferenced warnings

	* atree.h: Add flags up to Flag247
	(Flag231): New macro.

From-SVN: r130815