“… Advance refundings—whereby government entities essentially refinance existing debt at better interest rates, but before the original bond matures—were eliminated in the revised tax code. … Government authorities also have found ways to refinance non-mature bonds within the confines of the more restrictive tax code … A ‘Cinderella refunding’ is essentially an advance refunding carried off by issuing debt as taxable and then converting it to tax-exempt debt. …”