Set a callback used to generate random bytes. By default, we use
the same function as passed to evdns_set_transaction_id_fn to generate
bytes two at a time. If a function is provided here, it's also used
to generate transaction IDs.
NOTE: This function has no effect in Libevent 2.0.4-alpha and later,
since Libevent now provides its own secure RNG.
Set a callback used to generate random bytes. By default, we use the same function as passed to evdns_set_transaction_id_fn to generate bytes two at a time. If a function is provided here, it's also used to generate transaction IDs.
NOTE: This function has no effect in Libevent 2.0.4-alpha and later, since Libevent now provides its own secure RNG.