Eliminate compiler warnings from IA-64 port.

Eliminate compiler warnings from IA-64 port.
	* coff-ia64.c (howto_table): Use EMPTY_HOWTO.
	(in_reloc_p): Add ATTRIBUTE_UNUSED to unused parameters.
	* cpu-ia64-opc.c (ins_rsvd, ext_rsvd, ins_const, ext_const): Likewise.
	(ins_imms_scaled): Initialize sign_bit at function entry.
	(elf64_ia64_operands): Add missing initializers.
	* elfxx-ia64.c (elfNN_ia64_reloc, elfNN_ia64_reloc_type_lookup,
	elfNN_ia64_info_to_howto, elfNN_ia64_fake_sections,
	elfNN_ia64_add_symbol_hook, elfNN_ia64_is_local_label_name,
	elfNN_ia64_local_hash_table_init, get_fptr, get_pltoff,
	elfNN_ia64_adjust_dynamic_symbol): Add ATTRIBUTE_UNUSED for unused
	parameters.
	(elfNN_ia64_info_to_howto): Initialize free_relocs, free_contents,
	and free_extsyms at function entry.
	(elfNN_add_symbol_hook): Add unsigned cast to bfd_get_gp_size result.
	(elfNN_ia64_create_dynamic_sections): Delete unused local h.
	(get_got): Delete unused local srel.
	(elfNN_ia64_check_relocs): Initialize dynrel_type when declared.
	(elfNN_ia64_relocate_section): Delete unused local dynindx.