[fmyojovu] initializing LFG with XOF

according to Wikipedia, "The initialization of [lagged Fibonacci pseudorandom number generators] is a very complex problem."

this seems a straightforward application for a cryptographic hash, in particular, an extendable output function such as SHAKE256.  we need it to be extendable in order to be able to keep sampling if the least significant bit of all initial state vector entries is zero.

previously on SHAKE256.

previously on seeding an RNG with the output of a hash function.