Unlike other variable allocation logic, MODULE allocation does
not depend on resolution. So in order to give hole check elimination
(which runs during resolution) access to the information "is this
variable an import", simply allocate all modules variables prior
to resolution.

BUG=v8:1569

Review-Url: https://codereview.chromium.org/2458653002
Cr-Commit-Position: refs/heads/master@{#40621}