The bytecode generator has special handling for comparing the result of
the typeof operator against a string literal. This needs to be adapted
for bigints.

R=jkummerow@chromium.org, mythrie@chromium.org

Bug: v8:6791
Change-Id: I42d6c9e9225ce05e19393f10e01ae496ecb70c9c
Reviewed-on: https://chromium-review.googlesource.com/753465
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49172}