Swap tables, flash-friendly swap, swap_ops, and more

I've been enjoying this renewed focus on memory efficiency. On my personal system, I've noticed that even with loads of memory, having a large swap partition really helps out when a big burst of memory demand comes up, like then running a large compile job. And that even hours or days after the memory demand is over, I still have gigabytes of memory sitting in the swap page—evidently the programs don't actually need to use that memory at all!