Decode rectangles in order if needed

Some encodings must be handled in the order they are received.
Make sure we respect this in the decode manager.
diff --git a/common/rfb/TightDecoder.cxx b/common/rfb/TightDecoder.cxx
index 24236db..ec329e4 100644
--- a/common/rfb/TightDecoder.cxx
+++ b/common/rfb/TightDecoder.cxx
@@ -46,7 +46,7 @@
 #include <rfb/tightDecode.h>
 #undef BPP
 
-TightDecoder::TightDecoder() : Decoder(DecoderPlain)
+TightDecoder::TightDecoder() : Decoder(DecoderOrdered)
 {
 }