Unescaping names in dot files generated by nitdoc seems causes the recent failures on jenkins.
The bug was present since the new nitdoc but expressed by #883 that exposes the name of the project in the dot-file:
* On Jenkins, multiple workspace are identified with a @. eq. `workspace@2`
* The name of a Nit project is the name of the directory
* Therefore the `dot` command aborted when an identifier with @ was found, thus did not produce a map file.
* Therefore nitdoc aborted on the opening of the map file (to include in the HTML)
Retated to #891
Pull-Request: #894
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>