LCL: TTreeView: set overlay if none is set

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42882 4005530d-fff6-0310-9dd1-cebe43e6787f
LCL: docs

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42883 4005530d-fff6-0310-9dd1-cebe43e6787f
IDE: unit dependencies: overlays for cycles

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42884 4005530d-fff6-0310-9dd1-cebe43e6787f