Add a "Auto-Submitted: auto-generated" header to notification emails sent by the plugin. This should prevent "out-of-office" auto-responders and similar software from responding to these emails.

The "Auto-Submitted" header is defined in RFC 3834. See here for more information:
http://tools.ietf.org/html/rfc3834#section-5

git-svn-id: https://plugins.svn.wordpress.org/broken-link-checker/trunk@841295 b8457f37-d9ea-0310-8a92-e5e31aec5664