Do not support user-defined name for enums
Do not support user-defined name for enums

Summary:
I planed to support user-defined fields for enum classes, but it turns
out too special and not worth to support.

Reviewed By: int3

Differential Revision: D13632784

fbshipit-source-id: 6a95e8398953c9008192d1588e8e5f31c97d2e37

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