[Mediawiki-l] Multiple wikis - dealing with cookies

[Sy Ali]

I've got some issues with multiple wikis timing out and forcing
multiple logins throughout the day.  They're all hosted on the same
machine in different subdirectories (for various reasons).

I do recall that there is some functionality to tweak how these wikis
create their cookies.. in theory they could all share the same one. 
I'm not sure where to begin looking for the answers so I thought I'd
ask.