lcl: initialize PageControl.PageIndex in handle creation instead of loaded. Fix issue when setting TabVisible after control is loaded

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41407 4005530d-fff6-0310-9dd1-cebe43e6787f
Remove DoCreateWnd. Move its code to CreateWnd
Commit missing part of 41407

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41408 4005530d-fff6-0310-9dd1-cebe43e6787f