Moved GetParent into WX_COMPAT_2_2 and exposed base GetParent in
that case too.
Replaced all lib/sample uses of wxTC::GetParent with GetItemParent.
Updated docs to suit.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18448 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775