Please get rid of SuperFastHash

[dave-andersen]

First, the license on the external superfasthash code I can find isn't GPL, it's a BSD-ish one. But if we're not using it, I'd rather not have it in there, and even hinting that there's GPLed code in the file is twitchy. I suggest that we rip out the compiled hashutil file and separate the original hash functions from other people into their constituent parts, each preserving their own original license unless we reimplement them on our own. I'm happy to do this if we want.

Alternately, we can just rip out everything except our own and TwoIndependentMultiplyShift. I think I'd rather do this.