Int 31 Fn 0002  P - DPMI 0.9+ - Segment To Descriptor                      [E]

   AX = 0002h
   BX = real mode segment

Return: CF clear if successful
       AX = selector corresponding to real mode segment (64K limit)
   CF set on error
       AX = error code (DPMI 1.0+) (8011h) (see AX=0000h)

Notes: multiple calls for the same real mode segment return the same selector
   the returned descriptor can never be modified or freed
   not supported by MS Windows 3.0 in Standard mode