lib/godoc/godoc.html: try Google hosted jQuery first, fallback to locally hosted one

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/6593078

lib/godoc/godoc.html

@@ -8,7 +8,8 @@
   <title>The Go Programming Language</title>
 {{end}}
 <link type="text/css" rel="stylesheet" href="/doc/style.css">
-<script type="text/javascript" src="/doc/jquery.js"></script>
+<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
+<script type="text/javascript">window.jQuery || document.write(unescape("%3Cscript src='/doc/jquery.js' type='text/javascript'%3E%3C/script%3E"));</script>
 <script type="text/javascript" src="/doc/godocs.js"></script>
 {{if .SearchBox}}
 <link rel="search" type="application/opensearchdescription+xml" title="godoc" href="/opensearch.xml" />