wxWindow, wxSizer or wxSizerSpacer (instead of containing either a pointer or
just wxSize for spacers) and implement IsShown() and Show() by forwarding it
to the appropriate pointer: this means that now you can directly hide/show
windows/sizers/spacers instead of having to pass by containing sizers
Show(child) method
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@32865 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
