GNOME Shell and Mutter Fix Touch Interaction and Pointer Emulation on Wayland

Mutter now presents the right refresh rate units on Wayland/KMS, forces two-finger scroll by default, and addresses a crash that occurred when XWayland was initialized. On the other hand, GNOME Shell 3.19.3 adds a fix for scaling of thumbnails in the window switcher when using the desktop environment on HiDPI displays, and makes sure that animated backgrounds are now being updated during timezone changes.