INT 15 - SYSTEM - POINTING DEVICE BIOS INTERFACE (PS) - SET DEVICE HANDLER ADDR
        AX = C207h
        ES:BX -> FAR user device handler
Return: CF set on error
            AH = status (see AX=C200h)
Note:   when the subroutine is called, it is passed the following values on
          the stack; the handler should return with a FAR return without
          popping the stack:
                WORD 1: status (see below)
                WORD 2: X data (high byte = 00h)
                WORD 3: Y data (high byte = 00h)
                WORD 4: 0000h
SeeAlso: INT 33/AX=000Ch

Bitfields for status:
 bits 15-8 reserved (0)
 bit 7  Y data overflowed
 bit 6  X data overflowed
 bit 5  Y data is negative
 bit 4  X data is negative
 bit 3  reserved (1)
 bit 2  reserved (0)
 bit 1  right button pressed
 bit 0  left button pressed

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