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/win/rfb_win32/SDisplay.h b/win/rfb_win32/SDisplay.h
index 1773b78..8e38edb 100644
--- a/win/rfb_win32/SDisplay.h
+++ b/win/rfb_win32/SDisplay.h
@@ -76,13 +76,15 @@
       virtual void terminate();
       virtual void queryConnection(network::Socket* sock,
                                    const char* userName);
+      virtual void handleClipboardRequest();
+      virtual void handleClipboardAnnounce(bool available);
+      virtual void handleClipboardData(const char* data);
       virtual void pointerEvent(const Point& pos, int buttonmask);
       virtual void keyEvent(rdr::U32 keysym, rdr::U32 keycode, bool down);
-      virtual void clientCutText(const char* str);
 
-      // -=- Clipboard
+      // -=- Clipboard events
       
-      virtual void notifyClipboardChanged(const char* text);
+      virtual void notifyClipboardChanged(bool available);
 
       // -=- Display events