Add support for ELF files which contain multiple reloc sections which all target...

Add support for ELF files which contain multiple reloc sections which all target the same section.

	* elf-bfd.h (struct elf_backend_data): Add new fields:
	init_secondary_reloc_section, slurp_secondary_reloc_section,
	write_secondary_reloc_section.
	(_bfd_elf_init_secondary_reloc_section): Prototype.
	(_bfd_elf_slurp_secondary_reloc_section): Prototype.
	(_bfd_elf_write_secondary_reloc_section): Prototype.
	* elf.c ( bfd_section_from_shdr): Invoke the new
	init_secondary_reloc_section backend function, if defined, when a
	second reloc section is encountered.
	(swap_out_syms): Invoke the new symbol_section_index function, if
	defined, when computing the section index of an OS/PROC specific
	symbol.
	(_bfd_elf_init_secondary_reloc_section): New function.
	(_bfd_elf_slurp_secondary_reloc_section): New function.
	(_bfd_elf_write_secondary_reloc_section): New function.
	(_bfd_elf_copy_special_section_fields): New function.
	* elfcode.h (elf_write_relocs): Invoke the new
	write_secondary_relocs function, if defined, in order to emit
	secondary relocs.
	(elf_slurp_reloc_table): Invoke the new slurp_secondary_relocs
	function, if defined, in order to read in secondary relocs.
	* elfxx-target.h (elf_backend_copy_special_section_fields):
	Provide a non-NULL default definition.
	(elf_backend_init_secondary_reloc_section): Likewise.
	(elf_backend_slurp_secondary_reloc_section): Likewise.
	(elf_backend_write_secondary_reloc_section): Likewise.
	(struct elf_backend_data elfNN_bed): Add initialisers for the new
	fields.
        * configure.ac (score_elf32_[bl]e_vec): Add elf64.lo
        * configure: Regenerate.