Using atom elements in RSS feed

[Necoro]

Stackoverflow uses Atom's author tags in their RSS feed (cf.
https://stackoverflow.com/jobs/feed). They indeed use the correct namespace for it. But currently, as this namespace is unknown, it is just added as a random extension.

My wishful expected behavior would be to fill the author information of the RSS-feed structure.

I could implement it, but I want to ask beforehand:

1. Should this be done on a case-by-cases basis, read: for the moment only for the author tag.
2. In a general way: Allow atom tags in all possible places. This will probably turn out to be quite a lot of work (and messy?)
3. Ignore it, chimera feeds are evil :)

[Necoro]

Ok, special atom handling in RSS is already done for link, so I'll do the same for author.

While at it, I'll incorporate atom and atom03 into canonicalNamespaces to avoid having to guess by namespace prefix.