duplicate enum values don't work

[goertzenator]

Duplicated enum values in different enums such as the following do not work:

enum ZooAnimals {
   MONKEYS
   CATS
   BEARS
}

enum PetStoreAnimals {
   CATS  # uh oh
   DOGS
   PARROTS
}

A query involving zoo cats will produce an error like {invalid_enum_output,<<"ZooAnimals">>,<<"CATS">>}.

Duplicate enum values should be permitted as long as they all sit in different enums. The work around for now is to just ensure there are no duplicate enum values.

#91 talks about the enum table.