varnish plugin: Make argument "stats" const.

diff --git a/src/varnish.c b/src/varnish.c
index d0e6a80..357b5f1 100644 (file)
--- a/src/varnish.c
+++ b/src/varnish.c
@@ -216,7 +216,7 @@ static int varnish_submit_derive (const char *plugin_instance, /* {{{ */
 } /* }}} int varnish_submit_derive */
 
 static void varnish_monitor (const user_config_t *conf, /* {{{ */
-               c_varnish_stats_t *stats)
+               const c_varnish_stats_t *stats)
 {
        if (conf->collect_cache)
        {