Support linker relaxation of new R_MMIX_PUSHJ_STUBBABLE relocs.

	Support linker relaxation of new R_MMIX_PUSHJ_STUBBABLE relocs.
	* elf64-mmix.c (MAX_PUSHJ_STUB_SIZE): New macro.
	(struct _mmix_elf_section_data): New member pjs.
	(mmix_set_relaxable_size, mmix_elf_get_section_contents): New
	functions.
	(elf_mmix_howto_table): New entry for R_MMIX_PUSHJ_STUBBABLE.
	(mmix_reloc_map): Ditto.
	(mmix_elf_relocate_section): Handle R_MMIX_PUSHJ_STUBBABLE.
	(mmix_final_link_relocate, mmix_elf_check_common_relocs): Ditto.
	(mmix_elf_perform_relocation): Ditto.  Don't mark parameter addr
	unused.
	(mmix_elf_check_relocs): Move early return to after
	mmix_elf_check_common_relocs call.
	(mmix_elf_symbol_processing): Fix cut-and-pasto in head comment.
	(_bfd_mmix_before_linker_allocation): Rename from
	_bfd_mmix_prepare_linker_allocated_gregs.  All referers changed.
	Arrange to set the initial relaxable size of sections.
	(_bfd_mmix_after_linker_allocation): Rename from
	_bfd_mmix_finalize_linker_allocated_gregs.
	(mmix_elf_relax_section): Relax a R_MMIX_PUSHJ_STUBBABLE reloc.
	(bfd_elf64_get_section_contents): Define.
	* reloc.c: Add ENUMX for BFD_RELOC_MMIX_PUSHJ_STUBBABLE.
	* libbfd.h, bfd-in2.h: Regenerate.