bug#8117: ln to /tmp is irreversible

[Křištof Želechovski]

== To reproduce: ==

  1. Find a file in /tmp owned by somebody else and not owned by you.  Say 
a.txt.
  2. { ln a.txt b1.txt; } # you created b.txt based on a.txt
  3. {  rm b1.txt; } # error: Operation not permitted.
  4. Go to step 2, replacing b1 by b2, and so on.
(  5. ??? )
(  6. Profit. )

== The conclusion ==
Allowing irreversible operations is a bad thing, and this is not a circumstance 
where an exception would be appropriate.  The tool ln should not allow the 
operator to create an entry he cannot delete.

== Workaround ==
Never put anything into /tmp.  Use /tmp/kde-$LOGNAME (or whatever your 
directory is) instead.

IMHO,
Chris