hixie: Make the 'parse a time-zone offset component' rules handle errors. (whatwg r4320)

hixie: Make the 'parse a time-zone offset component' rules handle
errors. (whatwg r4320)

http://dev.w3.org/cvsweb/html5/spec/Overview.html?r1=1.3455&r2=1.3456&f=h
http://html5.org/tools/web-apps-tracker?from=4319&to=4320

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RCS file: /sources/public/html5/spec/Overview.html,v
retrieving revision 1.3455
retrieving revision 1.3456
diff -u -d -r1.3455 -r1.3456
--- Overview.html	25 Oct 2009 00:39:26 -0000	1.3455
+++ Overview.html	25 Oct 2009 00:41:31 -0000	1.3456
@@ -3643,7 +3643,9 @@
 
      <li>If <var title="">sign</var> is "negative", then negate <var title="">timezone<sub title="">minutes</sub></var>.</li>
 
-    </ol></li>
+    </ol><p>Otherwise, fail.</p>
+
+   </li>
 
    <li><p>Return <var title="">timezone<sub title="">hours</sub></var>
    and <var title="">timezone<sub title="">minutes</sub></var>.</li>