bfd: add support for eBPF

bfd: add support for eBPF

This patch adds support to BFD for elf64-bpf, in both little-endian
and big-endian variants.

bfd/ChangeLog:

2019-05-23  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* configure.ac: Add bpf_elf64_le_vec and bpf_elf64_be_vec.
	* configure: Regenerated.
	* Makefile.am (ALL_MACHINES): Add cpu-bpf.lo.
	(ALL_MACHINES_CFILES): Add cpu-bpf.c.
	(BFD64_BACKENDS): Add elf64-bpf.lo.
	(BFD64_BACKENDS_CFILES): Add elf64-bpf.c.
	* Makefile.in (SOURCE_HFILES): Regenerate.
	* config.bfd (targ_cpu): Handle bpf-*-* targets.
	* cpu-bpf.c: New file.
	* elf64-bpf.c: Likewise.
	* targets.c (_bfd_target_vector): Add bpf_elf64_be_vec and
	bpf_elf64_le_vec.
	* archures.c: Define architecture bfd_arch_bpf and machine
	bfd_arch_bpf.
	* reloc.c: Define BFD relocations used by the BPF target.
	* bfd-in2.h: Regenerated.
	* libbfd.h: Likewise.