Set Descriptor Access Rights

Modifies the access rights and type fields in the LDT
descriptor for the specified segment.

Call With:

   AX     = 0009H
   BX     = selector
   CL     = access rights/type byte
   CH     = 80386 extended access rights/type byte

Returns:

   if function successful
   Carry flag= clear

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8021H   invalid value (access rights/type bytes
                   invalid)
           8022H   invalid selector
           8025H   invalid linear address (changing the
                   access rights/type bytes would cause the
                   descriptor to reference a linear address
                   range outside that allowed for DPMI
                   clients.)

Notes:

o  The access rights/type byte passed to the function in CL
   has the following format:

   +---+---+---+---+---+---+---+---+
   | P |  DPL  | 1 |C/D|E/C|W/R| A |
   +-+-+---+---+-+-+-+-+-+-+-+-+-+-+
   |     |     |   |   |   |   |
   |     |     |   |   |   |   +- 0=not accessed, 1=accessed
   |     |     |   |   |   +----- data: 0=read,
   1=>read/write
   |     |     |   |   |          code: must be 1 (readable)
   |     |     |   |   +--------- data: 0=expand-up,
   1=expand-down
   |     |     |   |              code: must be 0
   (non-conforming)
   |     |     |   +------------- 0=data, 1=code
   |     |     +----------------- must be 1
   |     +----------------------- must equal caller's CPL
   +----------------------------- 0=absent, 1=present

   If the Present bit is not set in the descriptor, the DPMI
   host allows any values except in the DPL and "must be 1"
   bit fields.

o  On 80386 (and later) machines, the DPMI host interprets
   the value passed to the function in CH as follows:

   +---+---+---+---+---+---+---+---+
   | G |B/D| 0 |Avl|    Reserved   |
   +-+-+-+-+-+-+-+-+---+---+---+---+
   |   |   |   |         |
   |   |   |   |         +-- ignored
   |   |   |   +------------ can be 0 or 1
   |   |   +---------------- must be 0
   |   +-------------------- 0=default 16-bit, 1=default
   32-bit
   +------------------------ 0=byte granular, 1=page
   granular

o  A DPMI 1.0 host will reload any segment registers which
   contain the selector specified in register BX. It is
   suggested that DPMI 0.9 hosts also implement this.
o  Client programs should use the LAR instruction to examine
   the access rights of a descriptor.
o  Refer to the rules for descriptor usage in Appendix D.