* elf-bfd.h (elf_backend_data <elf_backend_hide_symbol>): Add
boolean param.
(_bfd_elf_link_hash_hide_symbol): Likewise.
* elflink.h (elf_link_add_object_symbols): Adjust call to
elf_backend_hide_symbol.
(elf_fix_symbol_flags): Likewise.
(elf_link_assign_sym_version): Likewise. Use bfd_malloc rather
than bfd_alloc.
* elf.c (_bfd_elf_link_hash_hide_symbol): Add "force_local" param.
Set ELF_LINK_FORCED_LOCAL and call _bfd_elf_strtab_delref.
* elf32-hppa.c (elf32_hppa_hide_symbol): Likewise.
(clobber_millicode_symbols): Adjust to suit new hide_symbol.
* elf32-cris.c (elf_cris_hide_symbol): Add "force_local" param
and adjust to suit.
* elf32-mips.c (_bfd_mips_elf_hide_symbol): Likewise, and call
_bfd_elf_link_hash_hide_symbol rather than duplicating code.
* elfxx-ia64.c (elfNN_ia64_hash_hide_symbol): Likewise.