compositor-wayland: split backend_init

Extract configuration parsing from init_backend function. The new
init_backend start by generating the configuration structure from
configuration file with separated function and then use this structure
to load the backend.

Signed-off-by: Benoit Gschwind <gschwind@gnu-log.net>
[Pekka: rebased]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed