Since there is a native C type for 64-bit integers (*int64_t), we can
just add support for them. Support for larger enums (u128) are currently
unstable and don't have a reasonable (standard-enough) C representation
to support at the moment.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

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.

…onflicting and non-conflicting deps.

Lockfile v2 only includes version numbers if they're conflicting.

Fixes #436