INT B3 - ZIPKEY - GET VERSION
        AH = 70h
Return: AH = major version
        AL = minor version
        CL = number of states and territories in current database
        DH = year of current database - 1900
        DL = month of current database's file date
Return: AX destroyed
Notes:  if installed, the string "ZIPKEY" is present at offset 75h in the
          interrupt handler's segment, and the byte at 7Bh contains the API
          version number (00h for v1.x, 01h for v2.0)
        ZIPKEY is a resident ZIPCODE database by Eric Isaacson