Merged r17441 into 3.20 branch.

Cherrypick of V8 3.20 r17658.

Fix uint32-to-smi conversion in Lithium

BUG=chromium:309623
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/70333002

Bug: 11684308
Change-Id: I6887c0c74faac0681bf19ffd1e4d8888de5c1bfe
git-svn-id: http://v8.googlecode.com/svn/branches/3.20@17658 ce2b1a6d-e550-0410-aec6-3dcde31c8c00