[Click] Core performance checkins

[Eddie Kohler]

Hi all,

This is just a note to say that I've merged the "coreperformance" branch 
with master.  There are several changes that may speed up particularly 
simple configurations, and that (more importantly) may make it easier to 
experiment with different multithreading setups.  (For instance I 
believe switching a task from one thread to another is faster now.)  Let 
me know if you experience any problems

Eddie