Enum alias support

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What steps will reproduce the problem?
1. Have 2 enums with the same value

What is the expected output? What do you see instead?
Would be nice to have an option to allow aliases (example, count enum with the 
same value as the last enum).
Something similar to the protocol-buffers 'option allow_alias = true;' in the 
Enum declaration.

Original issue reported on code.google.com by [e-mail] on 8 Jan 2014 at 5:25