the type of the callback and will invoke B<callback(a, b, gencb)> for new
style callbacks or B<callback(a, b, cb_arg)> for old style.
-It is possible to obtained the argument associated with a BN_GENCB structure
+It is possible to obtain the argument associated with a BN_GENCB structure
(set via a call to BN_GENCB_set or BN_GENCB_set_old) using BN_GENCB_get_arg.
BN_generate_prime() (deprecated) works in the same way as