INT 62 u - FGDRIVER v3.03 - "FG_KBTEST" - CHECK WHETHER SPECIFIED KEY PRESSED
        AX = 0054h
        BX = scan code of desired key
Return: AX = state
            0000h key is not pressed
            0001h key is currently pressed
Notes:  For FGDRIVER v1.10, this function was "FG_FLIPMASK" (see AX=002Ah);
          "FG_KBTEST" did not exist yet
        The low-level keyboard handler must have been enabled with AX=0053h
SeeAlso: AX=0053h,INT 16/AH=01h

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