This makes sure that the order of exports as they appear in asm.js
modules is maintained globally (not just per function) while being
translated to a WASM module.

R=clemensh@chromium.org
TEST=mjsunit/asm/asm-validation
BUG=chromium:720586

Change-Id: I8b26d717ae2f88467d41670bced901f196c7b3fc
Reviewed-on: https://chromium-review.googlesource.com/503708
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45277}