Allocate Specific LDT Descriptor

Allocates a specific LDT descriptor.

Call With:

   AX     = 000DH
   BX     = selector

Returns:

   if function successful
   Carry flag= clear

   and descriptor has been allocated
   if function unsuccessful
   Carry flag= set
   AX     = error code
           8011H   descriptor unavailable (descriptor is in
                   use)
           8022H   invalid selector (references GDT or
                   beyond the LDT limit)

Notes:

o  The first 10H (16) descriptors (selector values 04H-7CH)
   are reserved for this function and must not be used by
   the DPMI host.
o  Under DPMI 0.9 hosts, if another application has already
   been loaded, some of descriptors reserved for allocation
   by this function may be already in use and unavailable.
   Under DPMI 1.0 hosts, each client has its own LDT and
   thus will have the full 16 descriptors available for use
   with this function.
o  Resident service providers (protected-mode TSRs) should
   not use this function.
o  Refer to the rules for descriptor usage in Appendix D.