Important: License headers are now updated

[Jeremias Maerki <de...@jeremias-maerki.ch>]

I've just finished updating the license headers and the NOTICE file
based on http://www.apache.org/legal/src-headers.html

The announcement mail by Cliff Schmidt hasn't gone out, yet, but the
policy is already official. I guess some detail work will be necessary here
and there but that's it for today.

(Vincent, no need to alter the patch because of this. I'll take care of
it tomorrow. I just wanted to get this over with before opening the
branch.)

Jeremias Maerki
(who is sorry for flooding the commit list) ;-)