have numactl tell subprocesses that they are locked to a domain

[lm_mcvoy.com]

Summary

I'm wacking LMbench to be numa aware and this patch would help me make
sure that when you are a numa machine you could insist that people
run the benchmark via numactl.

Test Plan

Dunno, does FreeBSD have a test harness? Easy enough to add a little test that looks for the var.

[bcr]

You need to bump the .Dd in the man page to the date of the commit, since this is a content change.