Port Interlocked.cs from #982

https://github.com/bollhals/rabbitmq-dotnet-client/tree/channel

projects/RabbitMQ.Client/FrameworkExtension/Interlocked.cs

@@ -0,0 +1,31 @@
+// Note:
+// The code in this file is inspired by the code in `dotnet/runtime`, in this file:
+// src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/Interlocked.cs
+// 
+// The license from that file is as follows:
+//
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+
+
+using System.Runtime.CompilerServices;
+
+namespace RabbitMQ.Client
+{
+#if NETSTANDARD
+    // TODO GH-1308 class should be called "Interlocked" to be used by other code
+    internal static class InterlockedExtensions
+    {
+        public static ulong CompareExchange(ref ulong location1, ulong value, ulong comparand)
+        {
+            return (ulong)System.Threading.Interlocked.CompareExchange(ref Unsafe.As<ulong, long>(ref location1), (long)value, (long)comparand);
+        }
+
+        public static ulong Increment(ref ulong location1)
+        {
+            return (ulong)System.Threading.Interlocked.Add(ref Unsafe.As<ulong, long>(ref location1), 1L);
+        }
+    }
+#endif
+}