ULE vs. 4BSD in RELENG_7

[Josh Carroll]

> ffmpeg:  1:38.885
>
> sysbench: (4,8,12,16 threads respectively):
>    2221.93
>    2327.87
>    2292.49
>    2269.29
>
> And buildworld: 13m47.052s

I ran these after changing the slice value to 7 as well with this patch.

ffmpeg:  1:38.547

sysbench:
   2236.55
   2321.02
   2271.76
   2254.85

buildworld:  13m44.792s

So it looks like it makes very little difference with the new patch.
It slightly increases performance of 4 and 8 thread sysbench, and very
slightly the buildworld time, but not nearly as significant a change
as with the release ULE changing the slice value.

Is the other half of the context switch enhancements compatible with
this patch? The performance numbers are now very close for the other
benchmarks, and still quite a bit better for MySQL, so hopefully this
will help out for 7.1-RELEASE (I imagine it's too late for
7.0-RELEASE, right?). Stability wise, I have had zero problems (with
all the patches you've provided). :) So at least on this box, the
patch is stable and a great improvement. Thanks again for all your
efforts Jeff!

Josh