* object.cc (Sized_relobj::do_layout): Use constant invalid_address
	instead of -1U.
	(Sized_relobj::do_finalize_local_symbols): Likewise.
	(Sized_relobj::map_to_kept_section): Likewise.
	* object.h (Sized_relobj::invalid_address): New constant.
	(Sized_relobj::do_output_section_offset): Check for invalid_address
	and return -1ULL.
	* output.cc (Output_reloc::local_section_offset): Use constant
	invalid_address instead of -1U.
	(Output_reloc::get_address): Likewise.
	(Output_section::output_address): Change -1U to -1ULL.
	* output.h (Output_reloc::invalid_address): New constant.
	* reloc.cc (Sized_relobj::write_sections): Use constant
	invalid_address instead of -1U.
	(Sized_relobj::relocate_sections): Likewise.
	* symtab.cc (Symbol_table::sized_finalize_symbol): Handle symbol
	values for merge sections.
	* target-reloc.h (relocate_for_relocatable): Use constant
	invalid_address instead of -1U.