INT 2F - DPMI 0.9+ - GET VENDOR-SPECIFIC API ENTRY POINT
        AX = 168Ah
        DS:(E)SI = selector:offset of ASCIZ vendor name
Return: AL = status
            00h successful
               ES:(E)DI -> extended API entry point
            8Ah unsuccessful
Notes:  the vendor name is used to determine which entry point to return; it is
          case-sensitive
        available in protected mode only
        32-bit applications use ESI and EDI, 16-bit applications use SI and DI
        this call is present but not documented for DPMI 0.9

Vendor names:
 "MS-DOS"       ??? and 386MAX v6.00+
 "386MAX"       386MAX v6.00+