INT B3 - ZIPKEY - LOOK UP CITY AND STATE FOR ZIPCODE
        AH = 76h
        DX = zipcode region (0-999)
        CH = last two digits of zipcode (0-99)
        ES:DI -> buffer for name
Return: CF set on error
            AL = suggested state code, FFh if none
            ES:DI buffer filled with suggested city name
        CF clear if successful
            AL = ZIPKEY state code
            BX = area code (v2.0+)
            ES:DI points one byte beyond end of name
SeeAlso: AH=78h