INT 2F - DOS v5.0 DOSSHELL TASK SWITCHER - IDENTIFY INSTANCE DATA
        AX = 4B05h
        ES:BX = 0000h:0000h
        CX:DX -> task switcher entry point (see AX=4B02h)
Return: ES:BX -> startup info structure (see below) or 0000h:0000h
Notes:  called by task switcher
        clients with instance data should hook this call, pass it through to
          the previous handler with unchanged registers using a simulated
          interrupt.  On return, the client should create a startup info
          structure (see below), store the returned ES:BX in the "next"
          field, and return the address of the created structure in ES:BX
        all MSDOS function calls are available from within this call
SeeAlso: AX=4B02h

Format of startup info structure:
Offset  Size    Description
 00h  2 BYTEs   major, minor version of info structure (03h,00h)
 02h    DWORD   pointer to next startup info structure or 0000h:0000h
 06h    DWORD   0000h:0000h (ignored)
 0Ah    DWORD   ignored
 0Eh    DWORD   pointer to instance data records

Format of one instance data record in array:
Offset  Size    Description
 00h    DWORD   address of instance data (end of array if 0000h:0000h)
 04h    WORD    size of instance data