Breaking changes

- [protocols] Update `wayland-protocols` to version 1.20. Some arguments are replaced with their correct
  enum type (instead of a plain `u32`), making it a breaking change.

Additions

- [client] Clone implementation for `QueueToken`
- [client] implement `From<Main<I: Interface>>` impl for `Attached<I: Interface>`
- [client] std::fmt::Debug implementation for `Proxy`, `Attached`, `Main`
- [server] std::fmt::Debug implementation for `Resource`, `Main`
- [scanner] std::fmt::Debug implementation for `Event` and `Request`
- [protocols] Update `wlr-protocols` to commit `16a28885bc92869d8e589e725e7bf018432c47e4`. Adding the
  `wlr-output-management`, `wlr-output-power-management` and `wlr-virtual-pointer` protocol extensions.

Bugfixes

- [cursor] Fix crash when providing extra large or 0 sizes for cursor theme
- [sys] Use pkg-config for compile time linking (fixes FreeBSD build without dlopen)
- [scanner] Force the use of `proc_macro2` fallback implementation, so that the scanner doesn't panic
  when ran with `RUSTFLAGS="-Cpanic=abort"`.
- [client] Fix a crash when receiving an event with a dead object argument (can happen due to protocol races).