xwm: Redirect root window subwindows

xwayland no longer does this for us, we have to request it now
diff --git a/src/xwayland/xwayland.h b/src/xwayland/xwayland.h
index 3927078..77262e8 100644
--- a/src/xwayland/xwayland.h
+++ b/src/xwayland/xwayland.h
@@ -23,6 +23,7 @@
 #include <wayland-server.h>
 #include <xcb/xcb.h>
 #include <xcb/xfixes.h>
+#include <xcb/composite.h>
 #include <cairo/cairo-xcb.h>
 
 #include "../compositor.h"