Various performance improvements

Hello sho, 

Please review the following commits I made in branch 'jeremy-perf'.

2e555b355c97d4af6ba7bc7427d956dd3066e47e (2013-02-28 11:30:47 -0800)
New shepherd

c35b304bc6cad7f595a7e120a3d525229b2d28a1 (2013-02-27 22:49:41 -0800)
Stopping duplicate resolver instantiations for silent builds

R=sho