This puts lowering of {JSCreateClosure} operations behind a flag. For
now the benefit of inline allocating such closures is negligible, it
does increase code size, and breaks in combination with inlining based
on {SharedFunctionInfo}.

R=jarin@chromium.org
BUG=v8:2206

Review-Url: https://codereview.chromium.org/2636493002
Cr-Commit-Position: refs/heads/master@{#42331}