Added wxTreebook:

- added the control itself
- added protected wxBookCtrlBase::AllowNullPage() to accommodate it
- big changes to the sample to get rid of (most) ugly macros
- added XRC handler for the control
- added docs
- and wxUSE_TREEBOOK everywhere


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@35862 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/tsamples.tex

@@ -369,9 +369,9 @@ It replaces the old dynamic sample.
 
 This samples shows \helpref{wxBookCtrl}{wxbookctrloverview} family of controls.
 Although initially it was written to demonstrate \helpref{wxNotebook}{wxnotebook}
-only, it can now be also used to see \helpref{wxListbook}{wxlistbook} and
-\helpref{wxChoicebook}{wxchoicebook} in action. Test each of the controls, their
-orientation, images and pages using commands through menu.
+only, it can now be also used to see \helpref{wxListbook}{wxlistbook},
+\helpref{wxChoicebook}{wxchoicebook} and \helpref{wxTreebook}{wxtreebook} in action.
+Test each of the controls, their orientation, images and pages using commands through menu.