wayland: Fix coding style issues

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>

https://bugzilla.gnome.org/show_bug.cgi?id=723560
Fix scaling of pointer axis vectors

The vector of libinput and Wayland pointer axis events are in pointer
motion coordinate space. To convert to clutter's internal representation
the vectors need to be scaled to Xi2 scroll steps.

https://bugzilla.gnome.org/show_bug.cgi?id=723560
Release Clutter 1.19.2
Post-release version bump to 1.19.3