[Bro] define a variable name based on string in bro

[Jan Grashöfer]

> I wonder if O(1) is the case for reading from a table as well ?
> If so, what would be the benefit of using a bloom filter ?

Roughly said: You cannot store the actual data in a bloom filter. It is
a probabilistic data structure for membership testing only. Compared to
hash tables, bloom filters are very small and constant in space.

Jan