[SCM] ardour3/master: Update copyright file.

[Fabian Greffrath]

Am Donnerstag, den 19.09.2013, 14:57 +0200 schrieb Jonas Smedegaard: 
> If you (as is a possibly interpretation) mean to say that _generally_ it 
> is "a bit over-cautious" to only write into copyright file what one is 
> comfortable with the quality of, then I strongly disagree!

Nope. I meant to say that if the upstream author himself tells you the
license of a specific file, then it should go into the copyright file.

- Fabian