[turbofan] Enforce allocation of register for imull/mull.

R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/697073002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25066 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
[turbofan] Fix bug in Rangify.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/699603002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25067 ce2b1a6d-e550-0410-aec6-3dcde31c8c00