- Convert 	net.inet.ip.dummynet.curr_time 	net.inet.ip.dummynet.searches 	net.inet.ip.dummynet.search_steps   to SYSCTL_LONG nodes. It will prevent frequent wrap around on 64bit archs.
- Convert
	net.inet.ip.dummynet.curr_time
	net.inet.ip.dummynet.searches
	net.inet.ip.dummynet.search_steps
  to SYSCTL_LONG nodes. It will prevent frequent wrap around on 64bit archs.

- Implement simple mechanics for dummynet(4) internal time correction.
  Under certain circumstances (system high load, dummynet lock contention, etc)
  dummynet's tick counter can be significantly slower than it should be.
  (I've observed up to 25% difference on one of my production servers).
  Since this counter used for packet scheduling, it's accuracy is vital for
  precise bandwidth limitation.

  Introduce new sysctl nodes:
  net.inet.ip.dummynet.
    tick_lost		- number of ticks coalesced by taskqueue thread.
    tick_adjustment	- number of time corrections done.
    tick_diff		- adjusted vs non-adjusted tick counter difference
    tick_delta		- last vs 'standard' tick differnece (usec).
    tick_delta_sum	- accumulated (and not corrected yet) time
  			  difference (usec).

Reviewed by:	glebius
MFC after:	2 month

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