Add zwp_linux_explicit_synchronization_v1

This protocol enables explicit synchronization of asynchronous graphics
operations on buffers on a per-commit basis. Support is currently
limited to dmabuf buffers and dma_fence fence FDs.

Explicit synchronization provides a more versatile notification
mechanism for buffer readiness and availability, and can be used to
improve efficiency by integrating with related functionality in display
and graphics APIs.

This protocol is also useful in ChromeOS ARC++ (running Android apps
inside ChromeOS, using Wayland as the communication protocol), where it
can enable integration of the ChromeOS compositor with the explicit
synchronization mechanisms of the Android display subsystem.

Finally, the per-commit nature of the release events provided by this
protocol potentially offers a solution to a deficiency of the
wl_buffer.release event (see
https://gitlab.freedesktop.org/wayland/wayland/issues/46

).

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Daniel Stone <daniels@collabora.com>
[Pekka: dropped Reveman from maintainers]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>