Send lossless refresh even with pending updates

There might be parts of the screen that haven't changed and can
therefore be refreshed. Figure which parts these are and send just
those.
diff --git a/common/rfb/VNCServerST.h b/common/rfb/VNCServerST.h
index 9a1a44d..b7845dd 100644
--- a/common/rfb/VNCServerST.h
+++ b/common/rfb/VNCServerST.h
@@ -229,7 +229,7 @@
     void stopFrameClock();
     int msToNextUpdate();
     void writeUpdate();
-    bool checkUpdate();
+    Region getPendingRegion();
     const RenderedCursor* getRenderedCursor();
 
     void notifyScreenLayoutChange(VNCSConnectionST *requester);