Add native nuget.

Aaru6.Checksums/Native.cs

@@ -0,0 +1,41 @@
+using System.Runtime.InteropServices;
+
+namespace Aaru6.Checksums
+{
+    public static class Native
+    {
+        static bool _checked;
+        static bool _supported;
+
+        public static bool IsSupported
+        {
+            get
+            {
+                if(_checked)
+                    return _supported;
+
+                ulong version;
+                _checked = true;
+
+                try
+                {
+                    version = get_acn_version();
+                }
+                catch
+                {
+                    _supported = false;
+
+                    return false;
+                }
+
+                // TODO: Check version compatibility
+                _supported = version >= 0x06000000;
+
+                return _supported;
+            }
+        }
+
+        [DllImport("libAaru.Checksums.Native", SetLastError = true)]
+        static extern ulong get_acn_version();
+    }
+}