Crisis on Earth-Sandman updated

I have made an update to “Crisis on Earth-Sandman: The Uses of Continuity in Neil Gaiman's Sandman” (www.panix.com/~alexx/sandman.html), covering the (small amounts of) DC continuity used in Sandman: Overture. This update also includes a few corrections and expanded footnotes suggested by material in the last couple volumes of The Annotated Sandman.