Thread affinity masks should be limited when threads are created

[oaken-source]

Smog can be combined with numactl to fix the placement of threads:

numactl -C 48,52,56,60,64,68,72,76,80,84,88 --membind=8 ./smog -t 1 -k p -d 0

But numactl will just define an affinity mask for all threads, so they can still be migrated within their respective affinity masks. We should fix this up in code when the threads are created.