noop-renderer: zero-initialize struct

This ensures that all function pointers we do not fill in will be NULL.

I had a crash in the Xwayland test with
https://gitlab.freedesktop.org/wayland/weston/merge_requests/274 without this,
because import_dmabuf was garbage.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

libweston/noop-renderer.c

@@ -106,7 +106,7 @@ noop_renderer_init(struct weston_compositor *ec)
 {
 	struct weston_renderer *renderer;
 
-	renderer = malloc(sizeof *renderer);
+	renderer = zalloc(sizeof *renderer);
 	if (renderer == NULL)
 		return -1;