updated acknowledgments section

Folks,

Please review and suggest changes quickly if you don't agree with its
content.  If I left out someone (sorry), please send a mail to the list 
asking to be added. 

Note that this section risks to be moved to an appendix soon, so don't
panic :)

Thanks!

-jose

[1]
http://www.w3.org/2001/XKMS/Drafts/XKMS-PR-PUB/PR-PUB-xkms-part-1.html#Acknowledgments