Clacks Overhead Broadcaster

Adds the GNU Terry Pratchett message to the X-Clacks-Overhead header

This extension adds the X-Clacks-Overhead header to all request, a completely harmless addition but allows the requested server to acknowledge the message. Several web servers already carry the X-Clacks-Overhead header as a way to immortalise and remember those we have lost. X-Clacks-Overhead is a non-standardised HTTP header based upon the fictional work of the late, great, Sir Terry Pratchett, in particular the Discworld novel Going Postal and the Clacks towers. The header value defaults to GNU Terry Pratchett, the message breaks down as follows: G: Send the message onto the next Clacks Tower. N: Do not log the message. U: At the end of the line, return the message. In the novel, the nature of the 'GNU' code would keep the name of John Dearheart forever transmitting through The Clacks network so long as the network still existed, and we can do the same with the X-Clacks-Overhead header. "A man is not dead while his name is still spoken."