Rename EM_486 to EM_IAMCU

Rename EM_486 to EM_IAMCU

bfd/

	* elfcode.h (elf_object_p): Replace EM_486 with EM_IAMCU.

binutils/

	* dwarf.c (init_dwarf_regnames): Replace EM_486 with EM_IAMCU.
	* readelf.c (guess_is_rela): Likewise.
	(dump_relocations): Likewise.
	(get_machine_name): Likewise.
	(get_elf_section_flags): Likewise.
	(process_section_headers): Likewise.
	(is_32bit_abs_reloc): Likewise.
	(is_32bit_pcrel_reloc): Likewise.

include/elf/

	* common.h (EM_486): Renamed to ...
	(EM_IAMCU): This.