This unblocks avoiding the separate code template.
In the upcoming CL doing away with code templates, We need to track instances
through the module object, which needs to be separate from the compiled module
data, which is then shared with the first instance.

This CL ensures we have the object available in the asm.js scenario, too.

Note that this CL also unifies the error messaging when module
decoding fails.

BUG=v8:5316

Review-Url: https://codereview.chromium.org/2299873002
Cr-Commit-Position: refs/heads/master@{#39097}