[gtkmm] TreeView popup menu example

[Murray Cumming <murrayc usa net>]

I finally wrote a TreeView popup menu example in the gtkmm book, because
people ask about it so often [1]. Here are the bits in the book:
http://www.gtkmm.org/gtkmm2/docs/tutorial/html/ch08s06.html
and
http://www.gtkmm.org/gtkmm2/docs/tutorial/html/ch08s07.html#id2882346

But I remember some talk on the list about some flags that we could set
on the TreeView to allow button or keyboard events to be handled, or
something like that. Am I forgetting a simpler solution?

[1] Most recently,
http://bugzilla.gnome.org/show_bug.cgi?id=89780

-- 
Murray Cumming
murrayc usa net
www.murrayc.com