lto: Remap node order for stability.

lto: Remap node order for stability.

This patch adds remapping of node order for each lto partition.
Resulting order conserves relative order inside partition, but
is independent of outside symbols. So if lto partition contains
identical set of symbols, their remapped order will be stable
between compilations.

This stability is needed for Incremental LTO.

gcc/ChangeLog:

	* ipa-devirt.cc (ipa_odr_summary_write):
	Add unused argument.
	* ipa-fnsummary.cc (ipa_fn_summary_write): Likewise.
	* ipa-icf.cc (sem_item_optimizer::write_summary): Likewise.
	* ipa-modref.cc (modref_write): Likewise.
	* ipa-prop.cc (ipa_prop_write_jump_functions): Likewise.
	(ipcp_write_transformation_summaries): Likewise.
	* ipa-sra.cc (ipa_sra_write_summary): Likewise.
	* lto-cgraph.cc (lto_symtab_encoder_delete): Delete remap.
	(lto_output_node): Remap order.
	(lto_output_varpool_node): Likewise.
	(output_cgraph_opt_summary): Add unused argument.
	* lto-streamer-out.cc (produce_symbol_asm): Renamed. Use remapped order.
	(produce_asm): Rename. New wrapper.
	(output_function): Propagate remapped order.
	(output_constructor): Likewise.
	(copy_function_or_variable): Likewise.
	(cmp_int): New.
	(create_order_remap): New.
	(lto_output): Create remap. Remap order.
	* lto-streamer.h (struct lto_symtab_encoder_d): Remap hash_map.
	(produce_asm): Add order argument.