Enable Lockfree FEB Implementation By Default

[insertinterestingnamehere]

There's an option in our build system for lock-free FEBs that swaps in a lock-free hash table implementation. This seems like the kind of thing that we'd want on by default, but it's currently off. I'd like to try enabling it after I finish the current round of bugfixes to check that it's safe to enable it by default. From my initial look at it, it seems to be a working implementation. From there we can check the performance of the different implementations and decide which should be the default.