links to some of the transformation examples are broken

I was looking at the transformation examples on this page: https://spoon.gforge.inria.fr/examples.html

Some of the examples point to `https://gforge.inria.fr/scm/viewvc.php/trunk/spoon-examples/...` which gives me a 403 error.

I could find these broken examples (e.g. the visitor example) neither in this Github repository (https://github.com/INRIA/spoon) nor in the https://github.com/SpoonLabs/spoon-examples so I'm assuming they got lost somehow.

It would be great if the documentation could be fixed.

Start with the transformation examples page at spoon.gforge.inria.fr/examples.html and inspect the links using the old gforge.inria.fr paths. Compare the referenced examples with the INRIA/spoon and SpoonLabs/spoon-examples repositories to determine whether each link can be replaced or should be removed. Done means the page no longer points to inaccessible or missing transformation examples.

Written by the indexing model from the issue text.