- use `\cgalPckAuthor` in case of one author
- use of `\cgalPckAuthors` in case of multiple authors
- using in case of multiple authors always `, and `
- in the 1.9.6 `BaseDoxyfile.in` let the `\cgalPckAuthors` point to `\cgalPckAuthor` to get consistent output (not done for other versions as in the past the `ALIASES` could not call one another).