Perform on-demand global register allocation from

	Perform on-demand global register allocation from
	R_MMIX_BASE_PLUS_OFFSET relocs.
	* elf64-mmix.c (struct bpo_reloc_section_info, struct
	bpo_reloc_request, struct bpo_greg_section_info): New.
	(mmix_elf_check_common_relocs, mmix_elf_gc_sweep_hook,
	bpo_reloc_request_sort_fn, mmix_elf_relax_section,
	_bfd_mmix_check_all_relocs,
	_bfd_mmix_prepare_linker_allocated_gregs,
	_bfd_mmix_finalize_linker_allocated_gregs): New functions.
	(elf_mmix_howto_table): Correct src_mask for most relocs.
	(mmix_elf_perform_relocation) <case R_MMIX_BASE_PLUS_OFFSET>: New
	case.
	(mmix_final_link_relocate) <case R_MMIX_BASE_PLUS_OFFSET>: New
	case.  Fix typo in comment.  New label do_mmix_reloc.
	(mmix_elf_check_relocs): Abuse bfd_link_info member base_file to
	store first object file with a base-plus-offset reloc.  Call
	mmix_elf_check_common_relocs for the part common with mmo.
	(mmix_elf_final_link): Write out linker-allocated register
	contents section.
	(elf_backend_gc_sweep_hook): Define.
	(bfd_elf64_bfd_relax_section): Define.

	* mmo.c: Don't include <ctype.h>
	(mmo_init): Correct init-once logic.