Improve static_cfref_cast so that it can be used without causing an unnecessary retain/release in the case when one is only using the cast to convert to a more-derived raw CF ref type. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@47403 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775