How to hide column widget of treeview

[Markus Fischer <markus fischer name>]

Hi,

how can I hide the widget/column header of a column completely? I don't 
want a label or an empty label there, no space should be occupied.

Whatever I try to put into it with gtk_tree_view_column_set_widget, I 
can't get it to be completely removed. The best I get is still some 8 
pixel gap.

thanks,
- Markus