xsd-fu: extend copyright year range to 2013

It was done with the following shell command:

    git grep -l 'Copyright (C) [0-9]\{4\} - [0-9]\{4\}' | \
    xargs sed -i '' -e \
    's/\(Copyright (C) [0-9]\{4\} - \)[0-9]\{4\}/\12013/'
Merge pull request #687 from ctrueden/license-updates

License updates