[Ada] Expanded names in ghost assignments

[Ada] Expanded names in ghost assignments

gcc/ada/

	* ghost.adb (Whole_Object_Ref): New function to compute the name
	of the whole object.
	(Mark_And_Set_Ghost_Assignment): Rewrite to use
	Whole_Object_Ref.  We need to partly analyze the left-hand side
	in order to distinguish expanded names and record components.
	* lib-xref.ads, lib-xref.adb (Deferred_References): Move table
	to body, and add Defer_Reference to update the table, avoiding
	duplicates.
	(Generate_Reference): Avoid duplicates.
	* sem_ch8.ads, sem_ch8.adb (Find_Direct_Name): Remove _OK
	parameters, which are no longer needed. Ignore errors in
	Ignore_Errors mode.
	* sem_util.ads, sem_util.adb (Preanalyze_Without_Errors): Make
	this public, so we can call it from Ghost.
	* errout.ads, scng.adb, sem_prag.adb: Minor.