Mutter Window Manager Updated for GNOME 3.22 with Virtual Input Device Support

Mutter 3.22 Beta (technical version number is 3.21.90) re-adds support for edge scrolling on certain touchpads, implements support for trackball and mouse acceleration profiles, adds support for virtual input devices, and sets the correct output scale during hotplug. Among other improvements implemented in this first Beta release of Mutter 3.22, we can mention that monitor content is now being drawn to individual framebuffer, and the XDG_SESSION_TYPE variable is taken into consideration when attempting to determine the session type. Of course, numerous bugs have been squashed and parts of the code cleaned up.