RE: [security-services] SLO processing rules

Ok, I've uploaded core-3c and profiles-3c to correct the inconsistency.
Propagation (and in fact the overall logout operation really) is a SHOULD,
because that's what it's been in the actual logout processing rules. I just
changed the intro text, the new language, and the profile to match it.

The gist is that the SP can request logout, but the SA only has to listen,
it doesn't have to do it. It has to tell the SP what it did (Success vs
failure), but that's it.

Of course, it's a SHOULD, meaning not doing it is only intended for SAs with
special requirements.

-- Scott