Add ControllerInterface::Win32 to wrap XInput and DInput

Source/Core/InputCommon/ControllerInterface/Win32/Win32.h

@@ -0,0 +1,15 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+namespace ciface
+{
+namespace Win32
+{
+void Init();
+void PopulateDevices(void* hwnd);
+void DeInit();
+}
+}