Give subclasses the ability to overwrite the reader and writer

Needed for some tests.
diff --git a/common/rfb/CConnection.h b/common/rfb/CConnection.h
index 8bd886a..0109fe8 100644
--- a/common/rfb/CConnection.h
+++ b/common/rfb/CConnection.h
@@ -136,6 +136,9 @@
   protected:
     void setState(stateEnum s) { state_ = s; }
 
+    void setReader(CMsgReader *r) { reader_ = r; }
+    void setWriter(CMsgWriter *w) { writer_ = w; }
+
   private:
     // This is a default implementation of fences that automatically
     // responds to requests, stating no support for synchronisation.
diff --git a/common/rfb/SConnection.h b/common/rfb/SConnection.h
index da38b3e..fd6d263 100644
--- a/common/rfb/SConnection.h
+++ b/common/rfb/SConnection.h
@@ -184,6 +184,9 @@
   protected:
     void setState(stateEnum s) { state_ = s; }
 
+    void setReader(SMsgReader *r) { reader_ = r; }
+    void setWriter(SMsgWriter *w) { writer_ = w; }
+
   private:
     void writeFakeColourMap(void);