Reasonably large change to give us *exactly* correct NT delete on close semantics.

Reasonably large change to give us *exactly* correct NT delete on close semantics.
This was trickier than it looks :-). Check out the new DELETE_ON_CLOSE
flag in the share modes and the new code that iterates through all open
files on the same device and inode in files.c and trans2.c

Also changed the code that modifies share mode entries to take
generic function pointers rather than doing a specific thing so
this sort of change should be easier in the future.

Jeremy.