INT 62 u - FGDRIVER v3.03 - "FG_MOUSEBUT" - GET MOUSE BUTTON PRESS/RELEASE CNTS
        AX = 005Eh
        CX = mouse button (1 = left press, 2 = right press, 3 = middle press,
                          -1=left release, -2=right release, -3=middle release)
        ES:BX -> variable pointer record (see below)
Return: variables updated
Notes:  For FGDRIVER v1.10, this function was "FG_TCMASK" (see AX=00A5h);
          "FG_MOUSEBUT" was AX=007Ch
        This function returns the count of presses or releases since the last
          call to this function; if the count is zero, row and column will
          also be zero
SeeAlso: AX=005Fh,AX=0061h,AX=0064h

Format of variable pointer record:
Offset  Size    Description
 00h    WORD    segment of WORD buffer for press/release count
 02h    WORD    offset of WORD buffer for press/release count
 04h    WORD    segment of WORD buffer for screen space col of last press/rls
 06h    WORD    offset of WORD buffer for screen space col of last press/rels
 08h    WORD    segment of WORD buffer for screen space row of last press/rls
 0Ah    WORD    offset of WORD buffer for screen space row of last press/rls

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