1.1.3dev: The usernames in the default workflow hints are wrapped in `span`s with class `trac-author`. Refs #11699.

This is implemented by using `Chrome.authorinfo()` rather than `Chrome.format_author()`. Also:
 * `Chrome.authorinfo()` returns a span with class `trac-author-anonymous` and `trac-author-none` when the author is `anonymous` or `None`, respectively.
 * `Chrome.format_author()` returns `(none)` for any input that is //falsy//.
 * The `last` separator can be specified when calling `separated()`. The default is `None`, which preserves the previous behavior when `last` is not specified.


git-svn-id: http://trac.edgewall.org/intertrac/log:/trunk@13203 af82e41b-90c4-0310-8c96-b1721e28e2e2