* lto-streamer.c (lto_record_common_node): Don't track seen nodes,
	use lto_streamer_cache_append directly instead of returning a VEC.
	(preload_common_node): Remove.
	(lto_get_common_nodes): Rename to lto_preload_common_nodes, don't
	track seen nodes.
	(lto_streamer_cache_create): Call lto_preload_common_nodes.

Co-Authored-By: Richard Guenther <rguenther@suse.de>

From-SVN: r173956