Add the MD5 hash of null as a constant

BuildIRD/BuildIRD.cs

@@ -11,6 +11,7 @@ namespace BuildIRD
             byte[] discID = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
             byte[] discPIC = new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
             IRD ird = new IRD("Z:", discKey, discID, discPIC);
+            ird.Write("./ ird.ird");
             Console.WriteLine(ird.HeaderLength);
         }
     }

LibIRD/IRD.cs

@@ -20,6 +20,11 @@ namespace LibIRD
         /// 
         public static readonly byte[] Magic = new byte[] { 0x33, 0x49, 0x52, 0x44 };
 
+        /// <summary>
+        /// MD5 hash of null
+        /// </summary>
+        public static readonly byte[] NullMD5 = new byte[] {0xd4, 0x1d, 0x8c, 0xd9, 0x8f, 0x00, 0xb2, 0x04, 0xe9, 0x80, 0x09, 0x98, 0xec, 0xf8, 0x42, 0x7e};
+
         /// <summary>
         /// AES encryption/decryption keys and initial values
         /// </summary>
@@ -382,8 +387,6 @@ namespace LibIRD
                 {
                     // Keep track of the little-endian 32-bit "IEEE 802.3" CRC value
                     Crc32 crcStream = new Crc32();
-                    // TODO: Run as an async Task?
-                    crcStream.Append(outStream);
 
                     // Write IRD data to stream in order
                     using (BinaryWriter bw = new BinaryWriter(outStream))