Add support for Nuxi CloudABI on x86-64

Add support for Nuxi CloudABI on x86-64

bfd/

	* config.bfd (targ_defvec): Set to x86_64_elf64_cloudabi_vec
	for x86_64-*-cloudabi*.
	* configure.ac: Handle x86_64_elf64_cloudabi_vec.
	* configure: Regenerated.
	* elf64-x86-64.c (TARGET_LITTLE_SYM): Support x86_64-*-cloudabi*.
	(TARGET_LITTLE_NAME): Likewise.
	(ELF_OSABI): Likewise.
	(elf64_bed): Likewise.
	* targets.c (x86_64_elf64_cloudabi_vec): New.
	(_bfd_target_vector): Add x86_64_elf64_cloudabi_vec.

gas/

	* configure.tgt (fmt): Set to elf for *-*-cloudabi*.

ld/

	* Makefile.am (ALL_64_EMULATION_SOURCES): Add
	eelf_x86_64_cloudabi.c.
	(eelf_x86_64_cloudabi.c): New.
	* configure.tgt (targ_emul): Set to elf_x86_64_cloudabi for
	x86_64-*-cloudabi*.
	* Makefile.in: Regenerated.
	* emulparams/elf_x86_64_cloudabi.sh: New file.