NV: Implemented (with stubs) the vi:m service and some of its subservices.

The homebrew display test application now properly writes graphics data to the graphics buffer but we still don't have a way to compose the display layers.

src/core/hle/service/vi/vi.h

@@ -0,0 +1,34 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "core/hle/kernel/event.h"
+#include "core/hle/service/service.h"
+
+namespace Service {
+namespace VI {
+
+class IApplicationDisplayService final : public ServiceFramework<IApplicationDisplayService> {
+public:
+    IApplicationDisplayService();
+    ~IApplicationDisplayService() = default;
+
+private:
+    void GetRelayService(Kernel::HLERequestContext& ctx);
+    void GetSystemDisplayService(Kernel::HLERequestContext& ctx);
+    void GetManagerDisplayService(Kernel::HLERequestContext& ctx);
+    void OpenDisplay(Kernel::HLERequestContext& ctx);
+    void SetLayerScalingMode(Kernel::HLERequestContext& ctx);
+    void OpenLayer(Kernel::HLERequestContext& ctx);
+    void GetDisplayVsyncEvent(Kernel::HLERequestContext& ctx);
+
+    Kernel::SharedPtr<Kernel::Event> vsync_event;
+};
+
+/// Registers all VI services with the specified service manager.
+void InstallInterfaces(SM::ServiceManager& service_manager);
+
+} // namespace VI
+} // namespace Service