INT 33 - MS MOUSE v1.0+ - DEFINE INTERRUPT SUBROUTINE PARAMETERS
        AX = 000Ch
        CX = call mask (see below)
        ES:DX -> FAR routine
Notes:  when the subroutine is called, it is passed the following values:
          AX = condition mask (same bit assignments as call mask)
          BX = button state
          CX = cursor column
          DX = cursor row
          SI = horizontal mickey count
          DI = vertical mickey count
        in text modes, the row and column will be reported as a multiple of
          the cell size, typically 8x8 pixels
BUG:    some versions of the Microsoft documentation incorrectly state that CX
          bit 0 means call if mouse cursor moves, and swap the meanings of SI
          and DI
SeeAlso: AX=0018h

Bitfields for call mask:
 bit 0  call if mouse moves
 bit 1  call if left button pressed
 bit 2  call if left button released
 bit 3  call if right button pressed
 bit 4  call if right button released
 bit 5  call if middle button pressed (Mouse Systems/Logitech mouse)
 bit 6  call if middle button released (Mouse Sys/Logitech mouse)
 bits 7-15 unused

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