Deletes unused crankshaft implementation and C++ implementation,
which have been replaced by a CSA implementation.

BUG=v8:5977

Change-Id: I3614561e45db48583ee886461f98abb14cd9cc4f
Reviewed-on: https://chromium-review.googlesource.com/458418
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44018}