* docs/tutorial/C/gtkmm-tutorial-in.xml: Update the description of the Box
constructor. Mention set_homogeneous().
* docs/tutorial/C/figures/box_packing[1|2|3].png:
* examples/book/box/examplewindow.[h|cc]: Show set_homogeneous(true|false)
in the windows.
* examples/book/box/packbox.[h|cc]: Use Glib::ustring::format() instead of
sprintf().