preference caching

[Max Kalika]

Jon, I noticed that my preferences aren't being retreived from the session.  I 
looked in the mysql log and I get a select entry with every page load.  I 
verified that the session caching itself works, but the prefs don't get 
retreived.

I traced it down to the array_intersect line in tryCache() in Prefs.php.  Is 
there a reason for this?  I commented it out and it looks like its behaving as 
it should.  Only connection info gets put in the log and if prefs get changed, 
they are updated normally.

Thanks for any insight. :-)

--mk23