Change cppguide.xml to proper XML serialized HTML

cppguide.xml

@@ -1,9 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE html>
-<html>
+<html xmlns="http://www.w3.org/1999/xhtml">
 <head>
-  <meta charset="utf8">
-  <meta http-equiv="content-type" content="text/html;charset=utf-8">
-  <meta http-equiv="refresh" content="1; url=cppguide.html">
+  <meta http-equiv="refresh" content="1; url=cppguide.html"/>
   <title>Redirecting</title>
 </head>
 <!-- The BODY onLoad redirect is the best: it preserves #fragments and