simplified the code by using new wxClipboardSync class abstracting wait for clipboard results and wxScopeGuard to ensure that the 'waiting' flag is reset in every case

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45180 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/clipbrd.h

@@ -49,7 +49,10 @@ public:
     virtual void UsePrimarySelection(bool primary = TRUE)
         { m_usePrimary = primary; }
     
+
     // implementation from now on
+    // --------------------------
+
     bool              m_open;
     bool              m_ownsClipboard;
     bool              m_ownsPrimarySelection;
@@ -57,7 +60,6 @@ public:
 
     GtkWidget        *m_clipboardWidget;  /* for getting and offering data */
     GtkWidget        *m_targetsWidget;    /* for getting list of supported formats */
-    bool              m_waiting;          /* querying data or formats is asynchronous */
 
     bool              m_formatSupported;
     GdkAtom           m_targetRequested;