svn: annotate codec - bugfix

getCodec() needs to be called with an absolute file name.

As the changed decoding of the file contents will break the decoding of
svn's annotation prefixes (which are in system locale), force LC_ALL=C
to prevent an encoding mix in the first place.

Merge-request: 214
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>