sfeed_update: override fetch() example                                  [10/17]

The default rule in sfeed_update is:

	# fetch a feed via HTTP/HTTPS etc.
	# fetch(name, url, feedfile)
	fetch() {
        	# fail on redirects, hide User-Agent, timeout is 15 seconds.
	        curl -L --max-redirs 0 -H "User-Agent:" -f -s -m 15 \
        	        "$2" 2>/dev/null
	}

This uses curl to fetch data and outputs the XML data. This XML data will be
processed by the parse function.

