* elf-bfd.h (LEAST_KNOWN_OBJ_ATTRIBUTE): Define.

	* elf-bfd.h (LEAST_KNOWN_OBJ_ATTRIBUTE): Define.
	(struct elf_backend_data): Update comment on obj_attrs_order.
	* elf-attrs.c (vendor_obj_attr_size, vendor_set_obj_attr_contents,
	_bfd_elf_copy_obj_attributes): Use LEAST_KNOWN_OBJ_ATTRIBUTE
	instead of hardcoded 4.
	* elf32-arm.c (elf32_arm_obj_attrs_order): Use
	LEAST_KNOWN_OBJ_ATTRIBUTE and LEAST_KNOWN_OBJ_ATTRIBUTE + 1
	instead of hardcoded 4 and 5.
	(elf32_arm_merge_eabi_attributes): Use LEAST_KNOWN_OBJ_ATTRIBUTE
	instead of hardcoded 4.