Function nginx::RSA_meth_set_keygen

pub unsafe extern "C" fn RSA_meth_set_keygen(
    rsa: *mut RSA_METHOD, 
    keygen: Option<unsafe extern "C" fn(rsa: *mut RSA, bits: c_int, e: *mut BIGNUM, cb: *mut BN_GENCB) -> c_int>
) -> c_int