* elf.c (_bfd_elf_write_object_contents): Check for non-NULL

	* elf.c (_bfd_elf_write_object_contents): Check for non-NULL
	elf_shstrtab.
	* format.c (bfd_check_format_matches): Set output_has_begun
	for both_direction.
	* section.c (bfd_set_section_contents): Use bfd_write_p.  Remove
	special case for both_direction.