INT 2F - Ross Wentworth's Turbo Pascal POPUP LIBRARY
        AH = programmer-selected multiplex number
        AL = function
            00h installation check
                Return: AL = FFh if installed
            01h get TSR interrupt vectors
                Return: DX:AX -> vector table (see below)
            02h get TSR code segment
                Return: AX = code segment for all interrupt handlers
            03h call user exit routine and release TSR's memory
            04h get signature string
                Return: DX:AX -> counted string containing signature
            05h get TSR's INT 2F handler
                Return: DX:AX -> INT 2F handler
            06h enable/disable TSR
                BL = new state (00h disabled, 01h enabled)
            07h activate TSR (popup if not disabled)
            08h get hotkeys
                BL = which hotkey (00h = hotkey 1, 01h = hotkey 2)
                Return: AX = hotkey (AH = keyflags, AL = scancode)
            09h set hotkey
                BL = which hotkey (00h = hotkey 1, 01h = hotkey 2)
                CX = new hotkey (CH = keyflags, CL = scancode)
            0Ah-1Fh reserved

Format of vector table entry:
Offset  Size    Description
 00h    BYTE    vector number (00h = end of table)
 01h    DWORD   original vector
 05h    WORD    offset of interrupt handler in TSR's code segment