(Chapter 7 case involving IRA account balance of over $236,000 debtor claimed as exempt under 11 U.S.C. §522(b)(3)(C) and under state (MN) law; court’s opinion limited to federal exemption; debtor originally purchased annuity with funds rolled over from tax-qualified IRA that would have been exempt in bankruptcy; annuity complies with I.R.C. §408 and is exempt asset because it was purchased via direct rollover from another tax-exempt IRA).