Test mjsunit/wasm/compiled-module-serialization fails on those
architectures that do not support missaligned memory access.
We fix this by adding padding between code header and code start
in NativeModule serializer/deserializer so the code start is
properly aligned.

TEST=mjsunit/wasm/compiled-module-serializationx

Change-Id: I4f35b78a1190194088795b6f09becc3ad4251fdb
Reviewed-on: https://chromium-review.googlesource.com/1044186
Commit-Queue: Ivica Bogosavljevic <ivica.bogosavljevic@mips.com>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53117}