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

include/wx/msw/setup0.h

@@ -613,6 +613,14 @@
 // Recommended setting: 1
 #define wxUSE_CHOICEBOOK 1
 
+// wxTreebook control is similar to wxNotebook but uses wxTreeCtrl instead of
+// the tabs
+//
+// Default is 1.
+//
+// Recommended setting: 1
+#define wxUSE_TREEBOOK 1
+
 // wxTabDialog is a generic version of wxNotebook but it is incompatible with
 // the new class. It shouldn't be used in new code.
 //