INT 60 U - INTRSPY/CMDSPY API
Notes:  INTRSPY will hook the first available interrupt in the range 60h-67h.
        The installation check is to
          a) determine that the handler is an IRET instruction
          b) the signature 0Dh "INTRSPY vN.NN" immediately precedes the handler
          If INTRSPY is installed, the DWORD immediately after the IRET stores
          its entry point.
        INTRSPY is a script-driven debugger included with the book
          _Undocumented_DOS_.

Call INTRSPY entry point with:
        AH = function
            00h ???
            01h set current directory (for use in reporting)
                ES:DI -> counted string containing directory name (max 79 char)
            02h set name of script file
                ES:DI -> counted string containing file name (max 79 chars)
            03h set script arguments
                ES:DI -> counted string containing arguments (max 79 chars)
            04h get directory set with function 01h
                ES:DI -> 80-byte buffer for directory name
            05h get name of script file
                ES:DI -> 80-byte buffer for script filename
            06h get script arguments
                ES:DI -> 80-byte buffer for script arguments
            07h get ???
                CL = 00h-15h specifies what to get
                ES:DI -> WORD to be set with desired value on return
            08h get ???
                ES:DI -> WORD to be set with returned value
            09h get ???
                ES:DI -> WORD to be set with returned value
            0Bh store code for interrupt handler???
                ES:DI -> data
                CX = number of bytes
            0Ch ???
                ES:DI -> ???
            0Dh get ???
                ES:DI -> BYTE to be set with returned value
            0Eh set ??? flag
            0Fh clear ??? flag
            10h ???
                Return: AL = 04h or 05h if failed
            11h ???
                Return: AL = 05h if failed
            12h get ???
                ES:DI -> buffer
                Return: CX = number of bytes returned in buffer
            13h ???
Return: AH = 00h
        AL = status
            00h successful
            01h invalid function
            02h ???
            03h ???
            04h ???
            05h ???