Now that we have Wayland around, there's a whole branch of dependencies
that shouldn't be necessary anymore.
This allows to build KWin without all of it, allowing us to have a much
more compact alignment for cases where all the legacy software isn't
necessary anymore.
Bundle KWindowSystem X11-specific headers into it too, since it's part
of the same process.
Signed-off-by: Victoria Fischer <victoria.fischer@mbition.io>
