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>
diff --git a/src/text-backend.c b/src/text-backend.c
index 743cbc4..0c000ba 100644
--- a/src/text-backend.c
+++ b/src/text-backend.c
@@ -1026,11 +1026,12 @@
 static void
 text_backend_configuration(struct text_backend *text_backend)
 {
+	struct weston_config *config = wet_get_config(text_backend->compositor);
 	struct weston_config_section *section;
 	char *client;
 	int ret;
 
-	section = weston_config_get_section(text_backend->compositor->config,
+	section = weston_config_get_section(config,
 					    "input-method", NULL, NULL);
 	ret = asprintf(&client, "%s/weston-keyboard",
 		       weston_config_get_libexec_dir());