Added the field name to all CodedOutputStream.Write??? calls
Refactored 'speed' generated write of arrays to call Write???Array.  This may
have impacted speed write speeds for arrays of non-reference types due to the
use of non-generic IEnumerable and the subsequent boxing of value types.  This
could be addressed later if desired.
diff --git a/src/ProtocolBuffers/UnknownField.cs b/src/ProtocolBuffers/UnknownField.cs
index c403e8a..d3a7379 100644
--- a/src/ProtocolBuffers/UnknownField.cs
+++ b/src/ProtocolBuffers/UnknownField.cs
@@ -60,6 +60,7 @@
     /// </summary>

     public sealed class UnknownField

     {

+        public const string UnknownFieldName = "unknown_field";

         private static readonly UnknownField defaultInstance = CreateBuilder().Build();

         private readonly ReadOnlyCollection<ulong> varintList;

         private readonly ReadOnlyCollection<uint> fixed32List;

@@ -177,24 +178,24 @@
         {

             foreach (ulong value in varintList)

             {

-                output.WriteUInt64(fieldNumber, value);

+                output.WriteUInt64(fieldNumber, UnknownFieldName, value);

             }

             foreach (uint value in fixed32List)

             {

-                output.WriteFixed32(fieldNumber, value);

+                output.WriteFixed32(fieldNumber, UnknownFieldName, value);

             }

             foreach (ulong value in fixed64List)

             {

-                output.WriteFixed64(fieldNumber, value);

+                output.WriteFixed64(fieldNumber, UnknownFieldName, value);

             }

             foreach (ByteString value in lengthDelimitedList)

             {

-                output.WriteBytes(fieldNumber, value);

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

             }

             foreach (UnknownFieldSet value in groupList)

             {

 #pragma warning disable 0612

-                output.WriteUnknownGroup(fieldNumber, value);

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

 #pragma warning restore 0612

             }

         }