Run through unifdef(1) with slight hand-editing after. It is obvious,
that the driver is not going to be ever improved in terms of hardware
support, it is going to be only maintained as our kernel APIs change.
Carrying all the compatibility with ancient versions of NetBSD, OpenBSD,
Linux and BSDI, as well as obsoleted FreeBSD versions has no reason.
- Provide lmc_get_counter() to return counters that are not collected,
  but taken from hardware.
- Mechanically convert to if_inc_counter() the rest of counters.