Add support for wxDV_NO_HEADER to OS X/Cocoa wxDataViewCtrl.

Also use this flag with the tree control in the sample to test it and also
because it doesn't make much sense to have a single column without title
anyhow.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62601 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/dataview/dataview.cpp

@@ -604,7 +604,7 @@ void MyFrame::BuildDataViewCtrl(wxPanel* parent, unsigned int nPanel, unsigned l
             wxASSERT(!m_ctrl[3]);
             wxDataViewTreeCtrl* tc =
                 new wxDataViewTreeCtrl( parent, wxID_ANY, wxDefaultPosition,
-                                        wxDefaultSize, style );
+                                        wxDefaultSize, style | wxDV_NO_HEADER );
             m_ctrl[3] = tc;
 
             wxImageList *ilist = new wxImageList( 16, 16 );