Varnish plugin: Add a new plugin for reading values from Varnish, a web proxy server.

Hi list,

I created a new plugin to monitor a Varnish [1] instance.

So far the plugin monitor statistics about cache (hit/misses) and
connections but could monitor more in the future.

The patch is attached to this message, it has been generated against
the master branch of my local collectd copy.

Any feedback welcome

Have a nice day :)

Best Regards

1. http://varnish-software.com/

--
Jérôme

Signed-off-by: Florian Forster <octo@leeloo.lan.home.verplant.org>