Rename IFWL classes which do not have CFWL equivalents

xfa/fwl/core/ifwl_datetimeedit.h

-// Copyright 2014 PDFium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
-
-#ifndef XFA_FWL_CORE_IFWL_DATETIMEEDIT_H_
-#define XFA_FWL_CORE_IFWL_DATETIMEEDIT_H_
-
-#include <memory>
-
-#include "xfa/fwl/core/cfwl_widgetproperties.h"
-#include "xfa/fwl/core/fwl_error.h"
-#include "xfa/fwl/core/ifwl_edit.h"
-#include "xfa/fwl/core/ifwl_widget.h"
-
-class IFWL_DateTimeEdit : public IFWL_Edit {
- public:
-  IFWL_DateTimeEdit(const CFWL_App* app,
-                    std::unique_ptr<CFWL_WidgetProperties> properties,
-                    IFWL_Widget* pOuter);
-
-  // IFWL_Edit.
-  void OnProcessMessage(CFWL_Message* pMessage) override;
-
- private:
-  void DisForm_OnProcessMessage(CFWL_Message* pMessage);
-};
-
-#endif  // XFA_FWL_CORE_IFWL_DATETIMEEDIT_H_