Compact elf_backend_data

	* elf-bfd.h (struct elf_backend_data): Make arch, elf_osabi,
	elf_machine_code and target_os bitfields, and reorder.  Make
	maxpagesize, minpagesize, commonpagesize and p_align unsigned
	int.
	* elfxx-target.h (elfNN_bed): Reorder to suit.  Delete useless
	comments.