* lto-section-in.c: Add ext_symtab.
	* lto-streamer-out.c (write_symbol_extension_info): New.
	(produce_symtab_extension): New.
	(produce_asm_for_decls): Stream also produce_symtab_extension.
	* lto-streamer.h (enum lto_section_type): New section.
	* lto-symtab.h (enum gcc_plugin_symbol_type): New.
	(enum gcc_plugin_symbol_section_kind): Likewise.
	* lto-plugin.c (LTO_SECTION_PREFIX): Rename to ...
	(LTO_SYMTAB_PREFIX): ... this.
	(LTO_SECTION_PREFIX_LEN): Rename to ...
	(LTO_SYMTAB_PREFIX_LEN): ... this.
	(LTO_SYMTAB_EXT_PREFIX): New.
	(LTO_SYMTAB_EXT_PREFIX_LEN): New.
	(LTO_LTO_PREFIX): New.
	(LTO_LTO_PREFIX_LEN): New.
	(parse_table_entry): Fill up unused to zero.
	(parse_table_entry_extension): New.
	(parse_symtab_extension): New.
	(finish_conflict_resolution): Change type
	for resolution.
	(process_symtab): Use new macro name.
	(process_symtab_extension): New.
	(claim_file_handler): Parse also process_symtab_extension.
	(onload): Call new add_symbols_v2.