Fully converted over to ICodedOutputStream for all WriteTo derivations
diff --git a/src/ProtocolBuffers/UnknownField.cs b/src/ProtocolBuffers/UnknownField.cs
index d3a7379..edbbc29 100644
--- a/src/ProtocolBuffers/UnknownField.cs
+++ b/src/ProtocolBuffers/UnknownField.cs
@@ -174,7 +174,7 @@
         /// Serializes the field, including the field number, and writes it to

         /// <paramref name="output"/>.

         /// </summary>

-        public void WriteTo(int fieldNumber, CodedOutputStream output)

+        public void WriteTo(int fieldNumber, ICodedOutputStream output)

         {

             foreach (ulong value in varintList)

             {

@@ -238,11 +238,11 @@
         /// </summary>

         /// <param name="fieldNumber"></param>

         /// <param name="output"></param>

-        public void WriteAsMessageSetExtensionTo(int fieldNumber, CodedOutputStream output)

+        public void WriteAsMessageSetExtensionTo(int fieldNumber, ICodedOutputStream output)

         {

             foreach (ByteString value in lengthDelimitedList)

             {

-                output.WriteRawMessageSetExtension(fieldNumber, value);

+                output.WriteMessageSetExtension(fieldNumber, UnknownFieldName, value);

             }

         }