This adds support to get or set globals of all the standard types (i32,
i64, f32, f64).

R=titzer@chromium.org

Bug: v8:6600
Change-Id: Ie8d14d3d964e2abe3f19945a0e80b0e8462e9485
Reviewed-on: https://chromium-review.googlesource.com/969262
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52054}