The typer's ToNumber (and thus ToInteger etc.) returns type None when
the input type is BigInt, but we weren't quite ready for that in a few
places.

R=jarin@chromium.org

Bug: v8:7121
Change-Id: Ib12c726338f1ec3dfb9ba5cf54b00cc8d1351a89
Reviewed-on: https://chromium-review.googlesource.com/785130
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49604}