Bias commutative single-use register inputs and support lea adds

This improves register allocation for many common add and multiply patterns on ia32 and x64 by reducing register pressure.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/14856015

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14587 ce2b1a6d-e550-0410-aec6-3dcde31c8c00