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Remove mention of libgnomeui.
Use std::unique_ptr<> for workers queue.
Fix the strip view where only one item would be displayed or it would
crash. This is a bug caused by internal changes in GtkIconView between
3.2 and 3.4.

The ThumbStripView is now implementing Gtk::Orientable.
Use the "get_proxy()" directly for the RW property.
Use lambda where appropriate