* Change describe types to C ABI, check ext-php-rs version
Rust doesn't have a stable ABI so the describe function and types are
now C ABI compatible, however, the internal types `Cow`, `Vec`, `Option`
aren't.
Check `ext-php-rs` versions to check compatibility between the CLI and
the extension.
* CLI requires 0.7.1
* Bump versions
* Replace standard library types with ABI-stable replacements
* Change option type