codetools: fixed ForEachIdentifierInCleanSrc check if StartPos<1

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42728 4005530d-fff6-0310-9dd1-cebe43e6787f
IDE, SourceEditor: fix dragging editors between tab, make sure synedit will be set to visible

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42729 4005530d-fff6-0310-9dd1-cebe43e6787f