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/CMsgWriter.cxx b/common/rfb/CMsgWriter.cxx
index ddc25ff..0ebd33e 100644
--- a/common/rfb/CMsgWriter.cxx
+++ b/common/rfb/CMsgWriter.cxx
@@ -18,6 +18,7 @@
 #include <stdio.h>
 #include <rdr/OutStream.h>
 #include <rfb/msgTypes.h>
+#include <rfb/encodings.h>
 #include <rfb/PixelFormat.h>
 #include <rfb/Rect.h>
 #include <rfb/ConnParams.h>