Function nginx::BN_generate_prime

pub unsafe extern "C" fn BN_generate_prime(
    ret: *mut BIGNUM, 
    bits: c_int, 
    safe: c_int, 
    add: *const BIGNUM, 
    rem: *const BIGNUM, 
    callback: Option<unsafe extern "C" fn(arg1: c_int, arg2: c_int, arg3: *mut c_void)>, 
    cb_arg: *mut c_void
) -> *mut BIGNUM