[Click] Selector/timer change

[Eddie Kohler]

Hi all,

Just a heads up: The "threading" branch has been merged into mainline.  This 
branch changes the way timer sets and selector sets are handled on multicore 
machines, so that each core has its own set of each.  An element's selectors 
and timers are scheduled on the same thread that handles its Tasks.  (In the 
StaticThreadSched case.)  This has a couple benefits, including making locking 
behavior easier to understand.  Please let me know if you see any problems.

Eddie