This does three things:
1) It makes using es3 keywords and reserved words non fatal by default, it rewrites it to be a quoted property access.
2) It improves the error message displayed when a property like this is seen.
3) It introduces an ES3 diagnostic group that can be used to make these warnings errors again.

Fixes issue 1030
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=48372507