Committed in r320688

In the future when you find yourselves implementing synchronization primitives like swfw_sync or your hand rolled locks in if_bypass.c please make sure you get the attention and sign off from @markj, @jhb, or myself.

Also, can we stop massively refactoring the drivers until after the iflib version goes in to HEAD? And in general, there's a lot of non-productive function shuffling that goes on in Intel drivers that makes it a lot more work for downstream users maintaining their own branches.