Editors, Renderers and Attrs need to have a destructor so SWIG won't

Editors, Renderers and Attrs need to have a destructor so SWIG won't
complain about it, but since they are protected in C++ we need to give
them a dummy one.  In the future these shoud be changed to use
%ref/%unref and let SWIG manage the refcount for us.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38226 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775