UDPServer: Add configuration UI.

Accessed through button "Alternate Input Sources" in the "Controller Settings" dialog.

Source/Core/DolphinQt/Config/ControllerInterface/CemuHookUDPServerWidget.h

@@ -0,0 +1,26 @@
+// Copyright 2019 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <QWidget>
+
+class QCheckBox;
+class QLineEdit;
+class QSpinBox;
+
+class CemuHookUDPServerWidget final : public QWidget
+{
+  Q_OBJECT
+public:
+  explicit CemuHookUDPServerWidget();
+
+private:
+  void CreateWidgets();
+  void ConnectWidgets();
+
+  QCheckBox* m_server_enabled;
+  QLineEdit* m_server_address;
+  QSpinBox* m_server_port;
+};