Need to specify RDF xmlns in overlay. Fix for bug #15347. Suggested by waterson.

xpfe/global/resources/content/charsetOverlay.xul

@@ -8,6 +8,7 @@
 
 <overlay id="charsetOverlay"
 	xmlns:html="http://www.w3.org/TR/REC-html40"
+    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 	xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 
 <html:script language="JavaScript" src="chrome://global/content/charsetOverlay.js"/>