In the ideal case, this will speed up Object.create(null) by ~10x.

Drive-by-fix: Spread usage of new IsSpecialReceiverMap() and
              IsSpecialReceiverInstanceType(InstanceType) helpers.

BUG=v8:5788

Review-Url: https://codereview.chromium.org/2622723003
Cr-Commit-Position: refs/heads/master@{#42321}