Move credential native methods to their own file. Create a QueryNameSupport.cs file to hold a couple classes related to implementing that functionality.

Credentials/QueryNameSupport.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace NSspi.Credentials
+{
+    [StructLayout( LayoutKind.Sequential )]
+    public struct QueryNameAttribCarrier
+    {
+        public IntPtr Name;
+    }
+}