Another attempt at ProtoBuf serialization of Inventory

LibreMetaverse.Types/Vector4.cs

@@ -27,20 +27,26 @@
 using System;
 using System.Runtime.InteropServices;
 using System.Globalization;
+using ProtoBuf;
 
 namespace OpenMetaverse
 {
     [Serializable]
+    [ProtoContract]
     [StructLayout(LayoutKind.Sequential)]
     public struct Vector4 : IComparable<Vector4>, IEquatable<Vector4>
     {
         /// <summary>X value</summary>
+        [ProtoMember(1)]
         public float X;
         /// <summary>Y value</summary>
+        [ProtoMember(2)]
         public float Y;
         /// <summary>Z value</summary>
+        [ProtoMember(3)]
         public float Z;
         /// <summary>W value</summary>
+        [ProtoMember(4)]
         public float W;
 
         #region Constructors