LazControls: TExtendedTabControl added pages (runtime only)

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42607 4005530d-fff6-0310-9dd1-cebe43e6787f
IDE, lazbuild: on Unix change AllowDirectorySeparators to only /. File functions like ExtractFilePath/Name/Dir now ignore backslash \ as directory separator. The lazutils file functions already did that.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42608 4005530d-fff6-0310-9dd1-cebe43e6787f