PR binutils/2983

PR binutils/2983
* bfd/elf64-x86-64.c: Add FreeBSD support.
  (elf64_x86_64_fbsd_post_process_headers): New function.
* bfd/targets.c (_bfd_target_vector): Add bfd_elf64_x86_64_freebsd_vec.
* bfd/config.bfd (x64_64-*-freebsd*): Add bfd_elf64_x86_64_freebsd_vec to the targ_selvecs.
* bfd/configure.in: Add entry for bfd_elf64_x86_64_freebsd_vec.
* bfd/configure: Regenerate.
* gas/config/tc-i386.c (md_parse_option): Treat any target starting with elf64_x86_64 as a viable target for the -64 switch.
  (i386_target_format): For 64-bit ELF flavoured output use ELF_TARGET_FORMAT64.
* gas/config/tc-i386.h (ELF_TARGET_FORMAT64): Define.
* ld/emulparams/elf_x86_64_fbsd.sh (OUTPUT_FORMAT): Define as elf64-x86-64-freebsd.