Serializer: use opcode to signal new chunk.

src/serialize.h

Index: src/serialize.h
diff --git a/src/serialize.h b/src/serialize.h
index 36854b1de902491f05dac2da35750a2c3b91bf0e..3bb0e1a7a774d4a27bce03ece3797c61e4dd001b 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -377,6 +377,8 @@ class SerializerDeserializer: public ObjectVisitor {
 
   static const int kNop = 0xf;  // Do nothing, used for padding.
 
+  static const int kNextChunk = 0x4f;  // Move to next reserved chunk.
+
   static const int kAnyOldSpace = -1;
 
   // A bitmask for getting the space out of an instruction.