INT 2F U - DOS 3.3+ internal - CLOSE FILE
        AX = 1227h
        BX = file handle
        SS = DOS DS (must be using a DOS internal stack)
Return: CF set on error
            AL = 06h invalid file handle
        CF clear if successful
Notes:  can only be called from within DOS
        equivalent to INT 21/AH=3Eh
SeeAlso: AX=1201h,AX=1226h,INT 21/AH=3Eh