Update list of copyright holders, including contributors from 2012.

[[Imported from SVN: r1753]]

COPYING

 Copyright holders:
 
-2003--2008    Peter Bastian
+2003--2012    Peter Bastian
 2004--2012    Markus Blatt
 2004--2005    Adrian Burri
 2008          Andreas Dedner
-2003--2011    Christian Engwer
-2005--2011    Jorrit Fahlke
+2003--2012    Christian Engwer
+2005--2012    Jorrit Fahlke
 2008          Bernd Flemisch
 2005--2010    Carsten Gräser
 2012          Christoph Grüninger
 2012          Olaf Ippisch
 2004--2010    Robert Klöfkorn
 2009--2012    Andreas Lauser
+2012          Tobias Malkmus
 2007--2009    Sven Marnach
 2003--2005    Thimo Neubauer
-2010--2011    Rebecca Neumann
+2010--2012    Rebecca Neumann
 2012          Andreas Nüßing
 2008--2012    Martin Nolte
 2011          Elias Pipping