INT 21 U - DOS 4+ internal - COUNTRY-DEPENDENT FILENAME CAPITALIZATION
        AH = 65h
        AL = function
            A0h capitalize filename character
                DL = character to capitalize
                Return: DL = capitalized character
            A1h capitalize counted filename string
                DS:DX -> filename string to capitalize
                CX = length of string
            A2h capitalize ASCIZ filename
                DS:DX -> ASCIZ filename to capitalize
Return: CF set on error
            AX = error code (see AH=59h)
        CF clear if successful
Note:   nonfunctional in DOS 4.00 through 5.00 due to a bug (the code sets a
          pointer depending on the high bit of AL, but doesn't clear the
          bit before branching by function number).