The ES2015 spec is missing an extension of sloppy-mode block-scoped function
behavior to the global scope in scripts, as well as to eval. This patch
brings that hoisting to those two areas. The behavior is not perfectly
spec-compliant since properties created on the global scope should be
set as enumerable even if they are non-enumerable previously, but the
attributes will not be modified if the property already exists under
this patch.

BUG=v8:4441
LOG=Y
R=adamk
TEST=reddit comment functionality seems to be fixed

Review URL: https://codereview.chromium.org/1376623002

Cr-Commit-Position: refs/heads/master@{#31037}