The backend is prepared for managing multiple x11 windows. Currently
it's still only one window, but it's all internally working through
the architecture for multiple windows.
When pressing right control key the input gets grabbed/released.
The grab is for both keyboard and pointer and pointer is also confined
to the window.
How to grab/ungrab is added to the window title.
Each of the backends becomes a plugin. This allows kwin_wayland to load
the requested plugin and kwin itself doesn't need to link all the
libraries needed. E.g. libdrm is no longer linked if running kwin_x11.
Also this allows to create backends for the non-standard EGL platforms
(examples could be raspberrypi or Android devices).
The aim is to be able to create a plugin for each of the backends.
The following directories are created:
* backends/drm
* backends/fbdev
* backends/wayland
* backends/x11
