df-problems.c (df_kill_notes): Do not collect dead notes.

	* df-problems.c (df_kill_notes): Do not collect dead  notes.
	(df_set_note): Just call add_reg_note.
	(df_set_unused_notes_for_mw, df_set_dead_notes_for_mw,
	df_create_unused_note): Do not deal with lists of old notes.
	(df_note_bb_compute): Likewise.

From-SVN: r161708