Moves @child to the position after @sibling in the list of @box children.
If @sibling is %NULL, move @child to the first position.
the GtkWidget to move, must be a child of @box
the sibling to move @child after, or %NULL
See Implementation
Moves @child to the position after @sibling in the list of @box children.
If @sibling is %NULL, move @child to the first position.