1. corrected bug in MDI sample (which resulted in missing horz scrollbar)

1. corrected bug in MDI sample (which resulted in missing horz scrollbar)
2. define LVS_EX_FULLROWSELECT ourselves if compiler headers don't
3. wxSafeYield() will only reenable windows which had been enabled, not all
   windows in the application
4. selection in wxTreeCtrl is not broken after dnd operation
5. wxRegKey::Rename() added, regtest sample shows copying/moving/renaming keys
   and values now
6. wxListEvent accessors made const
7. wxListCtrl sets client data field in generated events under MSW too

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@6269 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775