This removes logic related to healing of the optimized code slot within
the feedback vector from the {FastNewClosure} builtin. The underlying
code will by now self-heal making it obsolete during closure creation.
It will also simplify future inline allocation of closures.

R=jarin@chromium.org
BUG=v8:6563

Change-Id: If57fe00e3a98c2af423a833c98a465a669b8f3bc
Reviewed-on: https://chromium-review.googlesource.com/649551Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47917}