INT 2F - Ergo DOS extenders - INSTALLATION CHECK
        AH = A1h
        BX = 0081h
        AL = which
            FEh OS/286,OS/386
            FFh HummingBoard DOS extender
        ES:DI -> 16-byte buffer
Return: if installed, first four bytes of ES:DI buffer are "IABH"
Note:   since TKERNEL is a licensed version, it is likely that subfunctions
          BX=0082h and BX=0084h are present and function identically to the
          AX=FBA1h/BX=008xh calls
SeeAlso: AX=FBA1h,INT 15/AX=BF02h