Add project files.

Compat.Private.Serialization/Compat/Runtime/FatalException.cs

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+using System;
+using System.Runtime.Serialization;
+
+namespace Compat.Runtime
+{
+    [Serializable]
+    internal class FatalException : SystemException
+    {
+        public FatalException()
+        {
+        }
+        public FatalException(string message) : base(message)
+        {
+        }
+
+        public FatalException(string message, Exception innerException) : base(message, innerException)
+        {
+            // This can't throw something like ArgumentException because that would be worse than
+            // throwing the fatal exception that was requested.
+            Fx.Assert(innerException == null || !Fx.IsFatal(innerException), "FatalException can't be used to wrap fatal exceptions.");
+        }
+
+        protected FatalException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}