Making it into more "idiomatic" Torque code (we are still defining what that means).
Template specialization on double and fast fixed arrays allowed me to cut
down on the boilerplate.

Bug: v8:7672
Change-Id: Ia35706993a9e2ea087ecc3ef93b3a5864ec97827
Reviewed-on: https://chromium-review.googlesource.com/1064054
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53246}