I noticed that Fortuna was explicitly zeroing the provided event in addition
to most callers. Pull the responsibility for zeroing events, which is
general to any conceivable algorithm, out of the algorithm-specific code and
into the callers. Most callers indirect through
random_fortuna_process_event(), so add the logic there.
Add one missing bzero in randomdev_accumulate(). Also, remove a redundant
bzero in the same function -- randomdev_hash_finish() is obliged to bzero
the hash state.