Wayland: Add support for pointer event frames

This adds support for wl_seat version 5, which adds pointer frames.
This allows two-dimensional scroll input to be emitted as single events
instead of one event per axis per motion.

It's also the the foundation for future enhancements like properly
scaled discrete scroll events and server-side key repeat.

Fixes #2494

CONTRIBUTORS.md

@@ -79,6 +79,7 @@ video tutorials.
  - Jason Francis
  - Gerald Franz
  - Mário Freitas
+ - Friz64
  - GeO4d
  - Marcus Geelnard
  - Gegy