It is better not to have V8-specific constants in mjsunit.js because it
also has V8-independent uses, e.g. in the spec tests.

R=gdeepti@chromium.org

Bug: v8:8015
Change-Id: I3b576f093f639c13e673cbd0bd5305c8101d7281
Reviewed-on: https://chromium-review.googlesource.com/1192843Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55485}