Unlock Linear Region


                 This function  unlocks a specified linear address range
                 that was previously locked using the Lock Linear Region
                 function.

            To Call

                 AX = 0601h
                 BX:CX = Starting linear address of memory to unlock
                 SI:DI = Size of region to unlock in bytes

            Returns

                 If function was successful:
                 Carry flag is clear.

                 If function was not successful:
                 Carry flag is set.

            Programmer's Notes

                 o    If this  function fails  then none  of the  memory
                      will be unlocked.
                 o    An error  will be  returned if  the memory was not
                      previously locked  or if  the specified  region is
                      invalid.
                 o    If the specified region overlaps part of a page at
                      the beginning  or end  of the  region, the page(s)
                      will be unlocked.
                 o    Even if  the function  succeeds, the  memory  will
                      remain locked if the lock count is not decremented
                      to zero.