Gtk::Button with image only

[Rob Benton <rob benton conwaycorp net>]

(I asked this on the glademm list too)

What's the easiest way to get a plain button with an image and no label?
 I'm still using Gtkmm 2.4 and I noticed there are a couple new methods
in Gtk::Button in 2.6 for images.  I've tried the ToolButton and I can't 
seem to set the label to 0 through the set_label method and get that to 
compile.