* hash.c (bfd_hash_allocate): Don't call bfd_set_error if

	* hash.c (bfd_hash_allocate): Don't call bfd_set_error if
	obstack_alloc returns NULL unless the size is non-zero.

	* linker.c (archive_hash_allocate): Define.
	(_bfd_generic_link_add_archive_symbols): Use archive_hash_allocate
	rather than obstack_alloc, for clarity.