Merge remote-tracking branch 'origin/topic/matthias/bloom-filter'

* origin/topic/matthias/bloom-filter:
  Add new BiF for low-level Bloom filter initialization.
  Introduce global_hash_seed script variable.
Changing the Bloom filter hashing so that it's independent of
CompositeHash.

We do this by hashing values added to a BloomFilter another time more
with a stable hash seeded only by either the filter's name or the
global_hash_seed (or Bro's random() seed if neither is defined).

I'm also adding a new bif bloomfilter_internal_state() that returns a
string representation of a Bloom filter's current internal state. This
is solely for writing tests that check that the filters end up
consistent when seeded with the same value.
Support UHF hashing for >= UHASH_KEY_SIZE bytes.