These functions clearly belong closer to respective classes
in wasm-objects.h.

R=clemensh@chromium.org

Bug: 
Change-Id: I46117b15181d33b237f4cdf318ce66ddb18d96bd
Reviewed-on: https://chromium-review.googlesource.com/684594Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48183}