This CL adds support for f32 locals and parameters, and implements the
basic f32 binary operations.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: Ia2d792dd1a6f7e97eab52a4ac49543b128fe3041
Reviewed-on: https://chromium-review.googlesource.com/796854Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49802}