You know you want you some Riverdance: In the opening "Reel Around the Sun," the stage throbs with a kind of orgiastic splendor.Some musicals continue to tour long after they've worn out their welcome. The orchestra grows thinner on each repeat visit, and the productions seem a little further removed from our initial memories. But I would expect Riverdance, which returns to the Fox this weekend for five performances between Friday and Sunday in what is being billed as the "farewell performances,
