GtkCTree::node_set_pixtext
    
     Sets the pixmap and the corresponding text of a column of a row.
     The pixmap and mask parameters may not be NULL.
    
    
     If you once expand/collapse the node, the icon is gone because the
     open/closed icons you set at the
     insert_node
     are used then. To prevent this, use the 
     set_node_info
     function. The text stays visible.