Wayland objects without wayland_crate feature

[mahkoh]

I want to access the libwayland pointers returned by gdk-wayland but I have no need for the dependencies pulled in by the wayland_crate feature.

I do not want to compile these dependencies and I do not want to spend effort unwrapping the returned objects just to get the pointers that were returned by gdk-wayland. I also do not want to use the C functions directly as it would require me to write additional unsafe code.

I do want to use thin safe wrappers that do nothing more than call the gdk functions and return the pointers.

[bilelmoussaoui]

Patches welcome