Push encoding specific formats into the encoders and decoders

Keep the generic stream classes clean and general.
diff --git a/common/rfb/TightDecoder.h b/common/rfb/TightDecoder.h
index 0b915f9..18b01f8 100644
--- a/common/rfb/TightDecoder.h
+++ b/common/rfb/TightDecoder.h
@@ -33,6 +33,8 @@
     virtual void readRect(const Rect& r, CMsgHandler* handler);
 
   private:
+    rdr::U32 readCompact(rdr::InStream* is);
+
     void tightDecode8(const Rect& r);
     void tightDecode16(const Rect& r);
     void tightDecode32(const Rect& r);