INT 31 P - DPMI 0.9+ - GET DESCRIPTOR
        AX = 000Bh
        BX = LDT selector
        ES:(E)DI -> 8-byte buffer for copy of descriptor
Return: CF clear if successful
            buffer filled
        CF set on error
            AX = error code (DPMI 1.0+) (8022h) (see AX=0000h)
Notes:  16-bit programs use ES:DI as pointer, 32-bit must use ES:EDI
        not supported by MS Windows 3.0 in Standard mode