GtkTreeView with 2 Columns

[Paolo <prallo gmail com>]

Hi at all! I have a problem about a tree with two columns. The first one is
a column that shows an icon and the second one shows a text. All works fine,
but between the columns I see an ugly vertical sperator. I know that there
are the style properties for each gtkWidget and in particular the
vertical-separator style property for my gtktreeview, but how can I set the
vertical-sperator?