input: make vnc use mouse mode notifiers

When we switch to absolute mode, we send out a notification (if the client
supports it).  Today, we only send this notification when the client sends us
a mouse event and we're in the wrong mode.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

vnc.h

@@ -168,6 +168,8 @@ struct VncState
     Buffer zlib_tmp;
     z_stream zlib_stream[4];
 
+    Notifier mouse_mode_notifier;
+
     QTAILQ_ENTRY(VncState) next;
 };