* elf-bfd.h (elf_backend_data): Add elf_backend_eh_frame_address_size.

	* elf-bfd.h (elf_backend_data): Add elf_backend_eh_frame_address_size.
	(_bfd_elf_eh_frame_address_size): Declare.
	* elfxx-target.h (elf_backend_eh_frame_address_size): Define a default.
	(elfNN_bed): Initialize elf_backend_eh_frame_address_size.
	* elfxx-mips.h (_bfd_mips_elf_eh_frame_address_size): Declare.
	(elf_backend_eh_frame_address_size): Define.
	* elfxx-mips.c (_bfd_mips_elf_eh_frame_address_size): New function.
	* elf-eh-frame.c (_bfd_elf_discard_section_eh_frame): Get the address
	size from the new backend hook.
	(_bfd_elf_write_section_eh_frame): Likewise.
	(_bfd_elf_eh_frame_address_size): New function.