Revert of Stage --harmony_sloppy_function (patchset #2 id:20001 of https://codereview.chromium.org/1393423002/ )

Reason for revert:
This still breaks Inbox.

Original issue's description:
> Stage --harmony_sloppy_function
>
> This patch turns on ES2015-style function hoisting semantics in
> staging. --harmony_sloppy_function was previously staged, leading
> to a number of bugs being filed and the staging being reversed;
> important bugs have been fixed, so it is time to try again.
>
> R=adamk
> LOG=Y
> BUG=v8:4285
>
> Committed: https://crrev.com/333e27fd99f8187c97e62b9538529900f0a30668
> Cr-Commit-Position: refs/heads/master@{#31190}

TBR=adamk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4285

Review URL: https://codereview.chromium.org/1402763003

Cr-Commit-Position: refs/heads/master@{#31206}