wxEnumProperty code is refactored in order to fix a hack which purpose was (apparently) to bypass constness of these functions by caching determined indices in wxEnumProperty::ms_nextIndex static member variable for further processing. (Unclear concept of using this static member was referred in http://trac.wxwidgets.org/ticket/12779#comment:9) Now, determined index is returned to the caller and processed there if necessary and hence caching of this index is not necessary. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78390 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775