Relicense all public domain modules to CC0.

I wrote all of most of them, for the others, here's the CCAN mailing
list thread authorizing it:

From: Timothy B. Terriberry <tterribe@xiph.org>
Subject: Re: [ccan] Changing from Public Domain to CC0
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: ccan@ozlabs.org
Date: Wed, 31 Oct 2012 02:53:50 -0400

Rusty Russell <rusty@rustcorp.com.au> wrote:

> I want to change the License string (and add a symlink) to the following
> trivial modules.  Please Ack.

> isaac

Ack.

From: Alessandro Guido <ag@alessandroguido.name>
Subject: Re: Changing from Public Domain to CC0
To: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 31 Oct 2012 10:59:53 +0100

Acked-by: Alessandro Guido <ag@alessandroguido.name>
From: Brad Hards <bradh@frogmouth.net>
Subject: Re: Changing from Public Domain to CC0
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Joey Adams <joeyadams3.14159@gmail.com>, Alessandro Guido <ag@alessandroguido.name>, Andreas Schlick <schlick@lavabit.com>, ccan@ozlabs.org
Date: Wed, 31 Oct 2012 23:43:24 +1100

On 31/10/12 17:43, Rusty Russell wrote:
> Damn lawyers!
>
> Since Public Domain is a slippery concept outside certain countries, it
> has been suggested that I formalize it to Creative Commons Zero.
>
> I want to change the License string (and add a symlink) to the following
> trivial modules.  Please Ack.

Ack.

More generally, anything I've put into CCAN is so trivial that you can
relicense it (to any Free / Open Source license) as part of any
relicensing you can otherwise get agreement to.

Brad

[Sorry if this comes out in HTML - I'm stuck with unsat tools while
travelling].

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>