Try making all memory pool and freelist code off by default, or clear-on-alloc
We've got mempool.c, and we've got freelists in buf_t. After recent shenanigans, it seems like a good idea to turn them off-by-default to see if any platforms actually need them, and have them on only when needed.
Additionally, we should look to see whether there's any performance hit that matters for making them get cleared before they're released.