Fix preference file pathname construction.

It was possible for the constructed preference file to have a slash in
its pathname-name, which signaled an error in CCL (and possibly
elsewhere) in a later pathname operation.

Fixes #107.
Output each manifest file entry only once.

Multiple entries could previously occur when a system with a slashed
name was encountered.
Merge slashes-in-manifest branch
Update version.txt to 2014-12-10. (Brown bag release.)