Allocate LDT Descriptors


                 This  function   is  used   to  allocate  one  or  more
                 descriptors from  the  task's  Local  Descriptor  Table
                 (LDT).  The descriptor(s) allocated must be initialized
                 by the application.

            To Call

                 AX = 0000h
                 CX = Number of descriptors to allocate

            Returns

                 If function was successful:
                 Carry flag is clear.
                 AX = Base selector

                 If function was not successful:
                 Carry flag is set.

            Programmer's Notes

                 o    If more than one descriptor was requested, AX will
                      contain  the   first  of  a  contiguous  array  of
                      descriptors.  You should add the value returned by
                      function 0003h (see function 0008H) to  get to the
                      next selector in the array.
                 o    The descriptor  will be  set to present data type,
                      with a base and limit of zero.
                 o    It is up to the caller to fill in the descriptors.
                 o    The privilege  level of descriptors will match the
                      application's code  segment privilege level.  When
                      modifying descriptors,  always set  the DPL to the
                      same  privilege   ring  as   your  program's  code
                      segment.  Use the lar instruction to determine the
                      privilege of a descriptor.