* cgraph.c (dump_cgraph_node): Dump alias flag.
	* cgraphunit.c (handle_alias_pairs): Handle weakrefs with no destination.
	(get_alias_symbol): New function.
	(output_weakrefs): Output also weakrefs with no destinatoin.
	(lto_output_node): Output weakref alias flag when at function boundary.

From-SVN: r180292