improve performance of list collection unser security

[GoogleCodeExporter]

What steps will reproduce the problem?
1. create a collection on a security-enabled instance of atombeat
2. add a thousand members
3. list the collection 

What is the expected output? What do you see instead?
xquery profiling shows that performance of list collection (in the absence of 
other plugins) is dominated by filtering the feed by permissions. can this go 
faster?

Original issue reported on code.google.com by alimanfoo@googlemail.com on 25 May 2011 at 11:09