[gtkmm] Adding a stock pixmap to a Gtk::ToggleButton

[Matthew Walton <matthew alledora co uk>]

I've been struggling with this for a while now, trying various variants
on making a Gtk::Image from the stock item and attempting to get it into
the ToggleButton. This doesn't work in a variety of
not-very-entertaining ways, including segfaulting and apparently
completely failing to get the stock item image into the Gtk::Image in
the first place. Therefore I have to ask: how do I get a stock pixmap
onto a Gtk::ToggleButton?

The absence of a ToggleButton constructor taking a StockID is a serious
pain here.

Thanks
-- 
Matthew Walton <matthew alledora co uk>