Only comparisons between const_iterator and iterator worked before (because of implicit conversion from the latter to the former), implement the ones in the other direction explicitly now. Closes #12594. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65857 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775