Constify more arrays

bfd/
	* coff-z80.c (bfd_howto_type): Make typedef const.
	* elf32-z80.c (bfd_howto_type): Likewise.
	* elf32-m32c.c (EncodingTable): Likewise.
	* elf32-csky.c (csky_arch_for_merge): Likewise.
	(csky_archs): Use typedef.
	* elf32-m68hc11.c (m68hc11_direct_relax_table): Make const.
	(find_relaxable_insn, m68hc11_elf_relax_section): Adjust to suit.
	* elf32-ppc.c (ppc_alt_plt): Make const.
	* elf32-rl78.c (relax_addr16): Likewise.
	* targets.c (_bfd_associated_vector): Likewise.
	(bfd_target_vector, bfd_associated_vector): Likewise.
	* libbfd-in.h (bfd_target_vector, bfd_associated_vector): Likewise.
	* libbfd.h: Regenerate.
include/
	* opcode/arc-attrs.h (CONFLICT_LIST): Make const.