Improved clipboard API

Change the internal clipboard API to use a request based model in
order to be prepared for more advanced clipboard transfers.
diff --git a/vncviewer/CConn.h b/vncviewer/CConn.h
index 38e09c2..4d935c9 100644
--- a/vncviewer/CConn.h
+++ b/vncviewer/CConn.h
@@ -61,8 +61,6 @@
 
   void bell();
 
-  void serverCutText(const char* str);
-
   void framebufferUpdateStart();
   void framebufferUpdateEnd();
   void dataRect(const rfb::Rect& r, int encoding);
@@ -74,6 +72,10 @@
 
   void setLEDState(unsigned int state);
 
+  virtual void handleClipboardRequest();
+  virtual void handleClipboardAnnounce(bool available);
+  virtual void handleClipboardData(const char* data);
+
 private:
 
   void resizeFramebuffer();