Refactor SerializationFormat::EndWrite and ChunkedIO::Chunk mem mgmt.

SerializationFormat::EndWrite now transfers ownership of the buffer
to the caller instead of doing a memcpy.

ChunkedIO::Chunk is no longer a POD type, hopefully the ctor/dtor
make it easier to manage its associated memory.  It also now
tracks how to deallocate its buffer (i.e. delete vs. free).

src/ChunkedIO.h

@@ -26,10 +26,27 @@ public:
 	ChunkedIO();
 	virtual ~ChunkedIO()	{ }
 
-	typedef struct {
+	struct Chunk {
+		typedef void (*FreeFunc)(char*);
+		static void free_func_free(char* data) { free(data); }
+		static void free_func_delete(char* data) { delete [] data; }
+
+		Chunk()
+		    : data(), len(), free_func(free_func_delete)
+			{ }
+
+		Chunk(char* arg_data, uint32 arg_len,
+		      FreeFunc arg_ff = free_func_delete)
+			: data(arg_data), len(arg_len), free_func(arg_ff)
+			{ }
+
+		~Chunk()
+			{ free_func(data); }
+
 		char* data;
 		uint32 len;
-	} Chunk;
+		FreeFunc free_func;
+	};
 
 	// Initialization before any I/O operation is performed. Returns false
 	// on any form of error.