ilog: relicense to Public Domain.

I noted to Timothy in 2011:
   I finally got around to implementing license checking in ccanlint,
   and it shows that your public domain ccan/isaac module uses your LGPL
   ccan/ilog module, which partially defeats the point.

   You and I are the only ones who did anything significant to ilog; I'm
   happy to relicense to PD or whatever else you want.  Or leave it, in
   which case I'll need to document it clearly.

He finally got back to me, and I sent him this patch, to which he replied:

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

ccan/ilog/LICENSE

-../../licenses/LGPL-2.1
+../../licenses/CC0
\ No newline at end of file

ccan/ilog/_info

@@ -29,7 +29,7 @@
  *    return 0;
  *  }
  *
- * License: LGPL (v2.1 or any later version)
+ * License: CC0 (Public domain)
  * Author: Timothy B. Terriberry <tterribe@xiph.org>
  */
 #include <string.h>

ccan/ilog/ilog.c

-/*(C) Timothy B. Terriberry (tterribe@xiph.org) 2001-2009 LGPL (v2 or later).
+/*(C) Timothy B. Terriberry (tterribe@xiph.org) 2001-2009 CC0 (Public domain).
  * See LICENSE file for details. */
 #include "ilog.h"
 #include <limits.h>

ccan/ilog/ilog.h

-/* Licensed under LGPLv2.1+ - see LICENSE file for details */
+/* CC0 (Public domain) - see LICENSE file for details */
 #if !defined(_ilog_H)
 # define _ilog_H (1)
 # include "config.h"