Oops, the hash function for fingerprints was terribly biased. There should

Oops, the hash function for fingerprints was terribly biased. There should
be XOR, not OR. Also, the shifts are meaningless, because the fingerprint
hash is believed to be very well distributed.

Beware, this means that the current mainline is incompatible with string
indices generated by v2.4!  For now, I'm not increasing the index version,
because word matching still works with old indices and I want to profile it.