compositor: migrate to stable viewporter.xml

Migrate from wl_scaler to wp_viewporter extension. The viewporter.xml
file is provided by wayland-protocols.

This stops Weston from advertising wl_scaler, and advertises
wp_viewporter instead.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
[Pekka: fix wayland-protocols requirement]
4 files changed