Swap a node with the other in this Tree

note: Nodes parents are updated, children still untouched

Property definitions

trees $ BinTreeMap :: transplant
	# Swap a `node` with the `other` in this Tree
	# note: Nodes parents are updated, children still untouched
	protected fun transplant(node, other: nullable N) do
		if node == null then return
		if node.parent == null then
			root = other
		else if node == node.parent.left then
			node.parent.left = other
		else
			node.parent.right = other
		end
		if other != null then other.parent = node.parent
	end
lib/trees/bintree.nit:237,2--249,4