Rework the subsurface tree by:
- forbidding subsurface loops
- storing the relative depth of a parent to its children,
finally respecting the wl_subsurface specification.
closes#23
* Rename priviledged to privileged in backend/drm/mod.rs
* Fix a number of typos in comments
* Fix typos in string literals
* Wrap identifiers with backticks in doc comments
* Spelling and capitalisation in doc comments
* Use XWayland in comments
This seems to be the standard capitalisation, even though the executable
is called `Xwayland`.
* Use Glium instead of glium in comments
* Use DRM and API in comments
* Fix remaining occurrence of 'priviledged'
* Reformat code to appease Travis' rustfmt