Add support for files that contain multiple symbol index tables. Fixes PR 15835

binutils	PR binutils/15835
	* readelf.c (struct elf_section_list): New structure.
	(symtab_shndx_hdr): Replace with symtab_shndx_list.
	(get_32bit_elf_symbols): Scan for a symbol index table matching
	the symbol table in use.
	(get_64bit_elf_symbols): Likewise.
	(process_section_headers): Handle multiple symbol index sections.

bfd	* elf-bfd.h (struct elf_section_list): New structure.
	(struct elf_obj_tdata): Replace symtab_shndx_hdr with
	symtab_shndx_list.  Delete symtab_shndx_section.
	(elf_symtab_shndx): Replace macro with elf_symtab_shndx_list.
	* elf.c (bfd_elf_get_syms): If symtab index sections are present,
	scan them for the section that matches the provided symbol table.
	(bfd_section_from_shdr): Record all SHT_SYMTAB_SHNDX sections.
	(assign_section_numbers): Use the first symtab index table in the
	list.
	(_bfd_elf_compute_section_file_positions): Replace use of
	symtab_shndx_hdr with use of symtab_shndx_list.
	(find_section_in_list): New function.
	(assign_file_postions_except_relocs): Use new function.
	(_bfd_elf_copy_private_symbol_data): Likewise.
	(swap_out_syms): Handle multiple symbol table index sections.
	* elf32-m32c.c (m32c_elf_relax_section): Replace use of
	symtab_shndx_hdr with use of symtab_shndx_list.
	* elf32-rl78.c (rl78_elf_relax_section): Likewise.
	* elf32-rx.c (rx_relax_section): Likewise.
	* elf32-v850.c (v850_elf_relax_delete_bytes): Likewise.
	* elflink.c (bfd_elf_final_link): Likewise.