The current Array.prototype.sort implementation is pretty sensitive to
compiler changes, i.e. switching to I+TF completely, so refactor it a
bit so that it can stay with FCG+CS for now.

Middle-term the Array builtins need to be refactored to TurboFan
builtins anyways.

BUG=chromium:670691,v8:5666
R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2553523002
Cr-Commit-Position: refs/heads/master@{#41471}