[Council] obsolete XEPs

[Peter Saint-Andre]

I just noticed that I have not yet updated XEP-0078 to reflect the
Council consensus to obsolete this spec (a decision made in the meeting
on 2008-10-08).

The Council did not have consensus to obsolete XEP-0090 and XEP-0091. If
there are no objections, I will extend the expiration dates on those
specs to 2008-12-31 so that we have until the end of the year to figure
out what we'll do with them.

Peter