This rewrites the rest property into a runtime call which sets up the
correct properties in the newly created object.

- Changes flag to --harmony-object-rest-spread
- Changes pattern rewriter to desugar rest property
- Adds new runtime function CopyDataPropertiesWithExcludedProperties

BUG=v8:5549

Review-Url: https://codereview.chromium.org/2620943002
Cr-Commit-Position: refs/heads/master@{#42430}