Use wxChoicebook instead of wxNotebook in the xrc sample.

Use wxChoicebook instead of wxNotebook in the xrc sample.

wxNotebook was unusable with so many pages under all platforms and completely
unusable under Mac. Replace it with wxChoicebook which allows to select any
page quickly instead of having to do it sequentially (or not being able to do
it at all under Mac).

Another possibility could be to use wxTreebook and organize the pages in
categories, similarly to how it is done in the widgets sample.

Closes #3699.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65891 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775