Array access fix: g++ darwin 4.2.1 compiler clamped array index to 0 when confronted with negative indices.

BUG=247303
R=jkummerow@chromium.org, ulan@chromium.org

Review URL: https://codereview.chromium.org/15855015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15038 ce2b1a6d-e550-0410-aec6-3dcde31c8c00