This adds support to constant-fold JSGetSuperConstructor(constructor)
for constructors with stable maps, i.e. where we can add a stability
dependency on the constructors map to get notified when the [[Prototype]]
of constructor changes.

R=petermarshall@chromium.org
BUG=v8:5517

Review-Url: https://codereview.chromium.org/2652763010
Cr-Commit-Position: refs/heads/master@{#42647}