wxClipboard::IsOpened() and wxCLipboardLocker helper class added

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@4105 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/clipbrd.h

@@ -39,6 +39,9 @@ public:
     // close the clipboard after SetData() and GetData()
     virtual void Close();
 
+    // query whether the clipboard is opened
+    virtual bool IsOpened() const;
+
     // set the clipboard data. all other formats will be deleted.
     virtual bool SetData( wxDataObject *data );