CVS commit by gebauer: 

Solution for the circular references problem.
This is achived by adding a check in KNRemoteArticle::setIdRef(), 
which prevents that an article references itself and a more sophisticated 
search for loops in KNGroup::buildThreads()

fixes #49903 and #50144


  M +4 -1      knarticle.h   1.11
  M +4 -4      knarticlemanager.cpp   1.77
  M +2 -4      kncleanup.cpp   1.31
  M +13 -14    kngroup.cpp   1.66