Add support for screenedge touchscreen events through XInput 2.2

Summary:
This change extends the XInputEventFilter to also listen for all touch
events on the root window.

The touch points are passed to the new gesture recognizer in screenedges.

Please note that I'm not using X11 and have hardly tested this change in
real world. To our X11 users with touch screen support: please test!

Test Plan: Can activate and deactivate the screenedge.

Reviewers: #plasma, #kwin

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D5137