tree.model. This should be called by
models when their rows have been reordered.gtkTreeModelRowsReordered(object, path, iter, new.order)objectpathGtkTreePath pointing to the tree node whose children have been
reorderediterGtkTreeIter pointing to the node whose children have been
reordered, or NULL if the depth of path is 0.new.ordernew.order[newpos] = oldpos.