This way it's more convenient for downstream crates like ostree-rs-ext
to convert loaded variants.
TODO: Can we add a feature for the `gvariant` crate and expose via
that too?
An intimidating spam of compiler errors at the start, but the
biggest was handling the new convention of `ostree_sys::` => `ffi::`.
This will require a semver bump of course.
Colin Walters
Felix Krull