compositor-wayland: Convert use-pixman flag to boolean

Signed-off-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
diff --git a/compositor/main.c b/compositor/main.c
index fca9778..d081106 100644
--- a/compositor/main.c
+++ b/compositor/main.c
@@ -1579,7 +1579,7 @@
 	config.display_name = NULL;
 	config.fullscreen = 0;
 	config.sprawl = 0;
-	config.use_pixman = 0;
+	config.use_pixman = false;
 
 	const struct weston_option wayland_options[] = {
 		{ WESTON_OPTION_INTEGER, "width", 0, &parsed_options->width },