If an error is thrown in a setTimeout callback, exit d8 with an error
code.
This will allow us to test asynchronous failures better, see linked bug.

R=yangguo@chromium.org
CC=mathias@chromium.org

Bug: v8:6981
Change-Id: Ifad152e6039f12dc4ceaac0bdc4b87f709898087
Reviewed-on: https://chromium-review.googlesource.com/738372Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49104}