Introduce wxCursorBase class defining common wxCursor API.

This is done in preparation for adding a new wxCursor method and will allow us
to define it in a single place by default instead of having to provide stubs
for all ports.

See #16539.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78133 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/qt/cursor.h

@@ -9,12 +9,11 @@
 #define _WX_QT_CURSOR_H_
 
 #include "wx/gdicmn.h"
-#include "wx/gdiobj.h"
 #include "wx/image.h"
 
 #include <QtGui/QCursor>
 
-class WXDLLIMPEXP_CORE wxCursor : public wxGDIObject
+class WXDLLIMPEXP_CORE wxCursor : public wxCursorBase
 {
 public:
     wxCursor() { }