compositor: remove the weston_config field in weston_compositor

The config can now be retrieved with a new function defined in weston.h,
wet_get_config(weston_compositor*).

Signed-off-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
10 files changed