Merge r269998 from head:
  - Count global pf(4) statistics in counter(9).
  - Do not count global number of states and of src_nodes,
    use uma_zone_get_cur() to obtain values.
  - Struct pf_status becomes merely an ioctl API structure,
    and moves to netpfil/pf/pf.h with its constants.
  - V_pf_status is now of type struct pf_kstatus.

  Submitted by: Kajetan Staszkiewicz <vegeta tuxpowered.net>
  Sponsored by: InnoGames GmbH