The second parameter of this method should be optional, so make it so in wxOSX. Also document what this method does exactly and the platforms under which it's implemented. Closes #13914. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70496 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775