/// <summary>
/// Make y a child of x.
/// </summary>
/// <param name="y">A node to become the child of x.</param>
/// <param name="x">A node to become the parent of y.</param>
protected void FibHeapLink(FHeapNode <T> y, FHeapNode <T> x)
{
y.Remove();
x.AddChild(y);
y.Mark = false;
}
