Added -x option to get XML output. As with the -1 option, it prints it once and quits...

Added -x option to get XML output. As with the -1 option, it prints it once and quits, and you can choose what fields to include with the -f option. Example XML output is

<?xml version="1.0"?>
<varnishstat timestamp="2009-02-25T08:45:02">
	<stat>
		<name>client_req</name>
		<value>2656016</value>
		<description>Client requests received</description>
	</stat>
</varnishstat>

varnishstat.xsd contains the XML schema for the output.

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@3824 d4fa192b-c00b-0410-8231-f00ffab90ce4