... mainly by adapting Object::Compare and
CodeStubAssembler::RelationalComparison.

TBR=rmcilroy@chromium.org

Change-Id: I34448d45b4950b9318263c4a667aa9db7d77232d
Bug: v8:6791
Reviewed-on: https://chromium-review.googlesource.com/730730
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48873}