Also move wxSeekMode from interface/wx/ffile.h to filefn.h to be consistent with the header in which this enum is really defined. And document it better. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70675 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775