HTTP/1.1 403 Forbidden header on a failed login

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Send an “HTTP/1.1 403 Forbidden” header on a failed login instead of “HTTP/1.1 200 OK”, which is the WordPress default header on failed login. This is a tremendously simple plugin that does only that and absolutely nothing else. The purpose of this plugin is to provide a way to allow external tools like fail2ban to get a message of a failed login e.g. to prevent a brute-force attack on a firewall level. For the public domain. Uses PHP5.3 anonymous functions and will not work on earlier versions of PHP