This option allows specifying that a C++ enum should be emitted with
plain `enum` rather than `enum class`. It's true that `enum class` should
generally be preferred, but sometimes there's existing code which is
already using plain `enum`, and porting that code to Rust becomes easier when
`cbindgen` can emit plain `enum`.
This option can be overridden on a per-enum basis using a `cbindgen:` annotation.
It defaults to true for two reasons:
* Backward compatibility.
* `enum class` is probably actually what you want, in general.
Evan Shaw
6a9066f7cd