Handle CopyRect like any other encoding

Avoids having to special case things. Keeps the code simpler.
diff --git a/common/rfb/CMsgWriter.cxx b/common/rfb/CMsgWriter.cxx
index 3d51060..6536eaf 100644
--- a/common/rfb/CMsgWriter.cxx
+++ b/common/rfb/CMsgWriter.cxx
@@ -113,9 +113,11 @@
   // Remaining encodings
   for (int i = encodingMax; i >= 0; i--) {
     switch (i) {
+    case encodingCopyRect:
     case encodingTight:
     case encodingZRLE:
     case encodingHextile:
+      /* These have already been sent earlier */
       break;
     default:
       if ((i != preferredEncoding) && Decoder::supported(i))