Function nginx::BN_GENCB_set_old

pub unsafe extern "C" fn BN_GENCB_set_old(
    gencb: *mut BN_GENCB, 
    callback: Option<unsafe extern "C" fn(arg1: c_int, arg2: c_int, arg3: *mut c_void)>, 
    cb_arg: *mut c_void
)