Set Segment Base Address

Sets the 32-bit linear base address field in the LDT
descriptor for the specified segment.

Call With:

   AX     = 0007H
   BX     = selector
   CX:DX  = 32-bit linear base address of segment

Returns:

   if function successful
   Carry flag= clear

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8022H   invalid selector
           8025H   invalid linear address (changing the base
                   would cause the descriptor to reference a
                   linear address range outside that allowed
                   for DPMI clients)

Notes:

o  A DPMI 1.0 host will automatically reload any segment
   register which contains the selector specified in
   register BX.  It is suggested that DPMI 0.9 hosts also
   implement this.
o  Refer to the rules for descriptor usage in Appendix D.