[4.1] bc81b85 Document what panic.clear -z does.

[Lasse Karstensen]

commit bc81b85ae9020924aa202388783559422ed3fceb
Author: Lasse Karstensen <lkarsten at varnish-software.com>
Date:   Fri Dec 4 11:29:58 2015 +0100

    Document what panic.clear -z does.

diff --git a/doc/sphinx/reference/varnish-cli.rst b/doc/sphinx/reference/varnish-cli.rst
index c55ecf8..390bbe9 100644
--- a/doc/sphinx/reference/varnish-cli.rst
+++ b/doc/sphinx/reference/varnish-cli.rst
@@ -133,7 +133,7 @@ panic.show
   Return the last panic, if any.
 
 panic.clear [-z]
-  Clear the last panic, if any.
+  Clear the last panic, if any. -z will clear related varnishstat counter(s).
 
 storage.list
   List storage devices.