Allow setting position of wxProgressDialog (wxMSW)

Position of wxProgressDialog cannot be changed directly because the dialog is created in another thread and may exist when SetPosition() is called. New position has be stored in the data structure used to share data between the main thread and the task dialog runner and the real update is done during the cyclic refresh in the dialog thread.

Closes #13546.

include/wx/msw/progdlg.h

@@ -42,6 +42,8 @@ public:
     virtual wxString GetTitle() const wxOVERRIDE;
 
     virtual void SetIcons(const wxIconBundle& icons) wxOVERRIDE;
+    virtual void DoMoveWindow(int x, int y, int width, int height) wxOVERRIDE;
+    virtual void DoGetPosition(int *x, int *y) const wxOVERRIDE;
 
     virtual bool Show( bool show = true ) wxOVERRIDE;