Placed back the 'orientation' and 'tc' values in the Ct default_value() method.
This change was proposed by Edward d'Auvergne in the following post:
https://mail.gna.org/public/relax-devel/2008-01/msg00005.html (Message-id:
<7f080ed10801080047nde3a3c8ucccd5f40ea7c21ea@...>)
