BFD64_LIBS, make the latter depending on the availability of BFD64.
Add archive64.c source file.
* archive64.c: New file implementing bfd_elf64_archive_slurp_armap
and bfd_elf64_archive_write_armap, code from elf64-mips.c
* archive.c (bfd_slurp_armap): Add ELF64 archive support.
* config.bfd (mips*-*-irix6*): Allow with BFD64 only.
(mips64*el-*-linux*): Likewise.
(mips*el-*-linux*): Likewise. Reorder entries.
* configure.in (bfd_libs): Define in dependency of BFD64 and
AC_SUBST it.
* elf64-mips.c (mips_elf64_slurp_armap): Remove, use
bfd_elf64_archive_slurp_armap instead.
(mips_elf64_write_armap): Remove, use bfd_elf64_archive_write_armap
instead.
