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.

src/probabilistic/Hasher.h

@@ -50,6 +50,15 @@ public:
 		return Hash(&x, sizeof(T));
 		}
 
+	/**
+	 * Computes hash values for an element.
+	 *
+	 * @param x The key of the value to hash.
+	 *
+	 * @return Vector of *k* hash values.
+	 */
+	digest_vector Hash(const HashKey* key) const;
+
 	/**
 	 * Computes the hashes for a set of bytes.
 	 *