to add_to_set to reloc. Remove bitsize argument from constructor.
Comment that reloc_overflow, reloc_dangerous and unattached_reloc
must handle NULL pointers for reloc location.
(enum bfd_link_order_type): Add bfd_section_reloc_link_order and
bfd_symbol_reloc_link_order.
(struct bfd_link_order): Add reloc field to union.
(struct bfd_link_order_reloc): Define.