INT 31H 0601H: Unlock Linear Region

                                                    Compatibility: DPMI 0.9+ 
 Expects: AX    0601H
          BX:CX starting linear address of memory to lock
          SI:DI size, in bytes, of region to lock
 Returns: CF    NC (clear) if successful; else AX = DPMI Error Code
    Info: Unlocks a region of linear memory that was previously locked via
          INT 31H 0600H (thereby allowing it to be moved around or swapped

          DPMI maintains a lock count.  The region is not unlocked until
          the lock count is decremented to 0.

See Also: DPMI API
          INT 2fH: Multiplex Interrupt
          DOS Functions