Support ATOM feeds.

[fischermx]

I'm trying to add this feed to the integrated vBulleting feeds reader:

http://googlemexicoblog.blogspot.com/atom.xml

It is a feed in ATOM format. I have not received an answer from vBulletin, but it seems this format is just not supported.
So, the modification is to support this format.

[rnmcd]

Are Atom feeds still not supported by vBulletin forums?