Get rid of the register mechanism for encoders and decoders

We have no use for it, so let's keep things simple.
diff --git a/common/rfb/TightDecoder.h b/common/rfb/TightDecoder.h
index 5cdf873..8200d2b 100644
--- a/common/rfb/TightDecoder.h
+++ b/common/rfb/TightDecoder.h
@@ -28,9 +28,9 @@
   class TightDecoder : public Decoder {
 
   public:
-    static Decoder* create(CMsgReader* reader);
-    virtual void readRect(const Rect& r, CMsgHandler* handler);
+    TightDecoder(CMsgReader* reader);
     virtual ~TightDecoder();
+    virtual void readRect(const Rect& r, CMsgHandler* handler);
 
   private:
     void tightDecode8(const Rect& r);
@@ -54,8 +54,6 @@
     void directFillRect16(const Rect& r, Pixel pix);
     void directFillRect32(const Rect& r, Pixel pix);
 
-    TightDecoder(CMsgReader* reader);
-
     CMsgReader* reader;
     CMsgHandler* handler;
     rdr::InStream* is;