Expects: AX    0003H
                                                                  
Returns: BX    Button status: bit 0 = left button down   (BX & 1) == 1
bit 1 = right button down  (BX & 2) == 2
bit 2 = center button down (BX & 4) == 4
CX    X coordinate (horizontal)    divide by 8 for text clm
DX    Y coordinate (vertical)      divide by 8 for text line
                                                                  
Info: This returns the current position of the mouse pointer, and the
current status of the mouse buttons.

Rather than constantly polling this function, many programmers
prefer to install a mouse event handler via INT 33H 000cH or
INT 33H 0018H and maintain global variables for instant access to
mouse information.

Notes: All X,Y coordinates are virtual coordinates and when working with
text mode, you must divide each value by 8 to get a character
clm,row.

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INT 33H 0003H: Query Position / Button Status