Align nixAC to spice2x folder structure

src/spice2x/launcher/shutdown.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <windows.h>
+#include <stdlib.h>
+#include <functional>
+
+namespace launcher {
+    extern std::function<void()> on_shutdown;
+    void stop_subsystems();
+    void kill(UINT exit_code = EXIT_FAILURE);
+    void shutdown(UINT exit_code = EXIT_SUCCESS);
+    void restart();
+}