This CL also adds the simplified operator NumberIsNaN.

Bug: v8:7340, v8:7250
Change-Id: Ifa44cf59b30ee700f7df61f8d58782a43fd0f3c5
Reviewed-on: https://chromium-review.googlesource.com/1023391Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52726}