Add xwayland-unmanaged.c

Handle xwayland override_direct surfaces separately from the view
struct - in order to simplify code, particularly in view.c

src/seat.c

@@ -0,0 +1,11 @@
+#include "labwc.h"
+
+void seat_focus_surface(struct wlr_surface *surface)
+{
+	if (!surface) {
+		wlr_seat_keyboard_notify_clear_focus(server.seat);
+		return;
+	}
+	/* TODO: add keyboard stuff */
+	wlr_seat_keyboard_notify_enter(server.seat, surface, NULL, 0, NULL);
+}