add support for custom controls in file dialog in wxGTK and generic versions; also allow using generic dialogs in the sample with wxGTK2 (patch 1846837)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52252 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/filedlg.h

@@ -30,8 +30,7 @@ public:
                  const wxPoint& pos = wxDefaultPosition,
                  const wxSize& sz = wxDefaultSize,
                  const wxString& name = wxFileDialogNameStr);
-
-    virtual ~wxFileDialog() {}
+    virtual ~wxFileDialog() { delete m_extraControl; }
 
     virtual wxString GetPath() const;
     virtual void GetPaths(wxArrayString& paths) const;
@@ -48,8 +47,8 @@ public:
     virtual void SetFilterIndex(int filterIndex);
 
     virtual int ShowModal();
-    virtual bool Show( bool show = true );
 
+    virtual bool SupportsExtraControl() const { return true; }
 
 
 protected: