INT 2F U - Quarterdeck - QEMM/QRAM/VIDRAM/MANIFEST v5.0+ - INSTALLATION CHECK
        AX = D200h
        BX = 5144h ("QD")
        CX = 4D45h ("ME")
        DX = 4D30h ("M0")
Return: AL = FFh installed
        if BX,CX,DX registers were as specified on entry:
            BX = 4D45h ("ME")
            CX = 4D44h ("MD")
            DX = 5652h ("VR")
Notes:  QEMM/QRAM/VIDRAM/MANIFEST/etc will search for a free AH value from D2h
          through FFh, then C0h through D1h
        for AL <> 0, if the BX/CX/DX values don't match a the identifier of a
          Quarterdeck product, it just chains to the previous INT 2F handler