INT 31 P - DPMI 0.9+ - ALLOCATE SPECIFIC LDT DESCRIPTOR
        AX = 000Dh
        BX = LDT selector
Return: CF clear if successful
            descriptor allocated
        CF set on error
            AX = error code (DPMI 1.0+) (8011h,8022h) (see AX=0000h)
Notes:  free descriptor with INT 31/AX=0001h
        the first 16 descriptors (04h-7Ch) are reserved for this function, but
          some may already be in use by other applications under DPMI 0.9;
          DPMI 1.0 guarantees 16 descriptors per client
        not supported by MS Windows 3.0 in Standard mode
SeeAlso: AX=0001h