[Bro-Dev] Bloom filter interface

[Matthias Vallentin]

> Is this merging bf2 into bf1? Would it make sense to return a new
> "opaque of bloomfilter" instead?

I was aiming for non-mutable semantics: the function leaves both bf1
and bf2 untouched, but merely returns bf1 + bf2, where "+" means union
of the underlying bit vectors. If this turns out to be a memory
problem after profiling, we could still add a void-returning in-place
merge function.

That said, we could also use the name "bloomfilter_unify" or
"bloomfilter_union", as we may end up with intersection at some point
(although I do not have a use case for it yet).

     Matthias