[tests] Add tests for AppDomainUnloadedException handling

As described on https://msdn.microsoft.com/en-us/library/system.appdomainunloadedexception(v=vs.110).aspx#Anchor_6

mono/tests/Makefile.am

@@ -469,6 +469,7 @@ TESTS_CS_SRC=		\
 	appdomain-unload-callback.cs	\
 	appdomain-unload-doesnot-raise-pending-events.cs	\
 	appdomain-unload-asmload.cs	\
+	appdomain-unload-exception.cs	\
 	unload-appdomain-on-shutdown.cs	\
 	bug-47295.cs	\
 	loader.cs	\
@@ -1905,7 +1906,8 @@ test-process-exit:
 
 # tests that expect a 1 exit code
 TESTS_UNHANDLED_EXCEPTION_1_SRC =	\
-	unhandled-exception-1.cs
+	unhandled-exception-1.cs	\
+	unhandled-exception-9.cs
 
 # tests that expect a 255 exit code
 TESTS_UNHANDLED_EXCEPTION_255_SRC =	\

mono/tests/appdomain-unload-exception.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+class Driver
+{
+	static void ThrowTP ()
+	{
+		ManualResetEvent mre = new ManualResetEvent (false);
+
+		ThreadPool.QueueUserWorkItem (_ => { try { throw new AppDomainUnloadedException (); } finally { mre.Set (); } });
+
+		if (!mre.WaitOne (5000))
+			Environment.Exit (1);
+
+		/* Wait for exception unwinding */
+		Thread.Sleep (500);
+	}
+
+	static void ThrowThread ()
+	{
+		Thread thread = new Thread (_ => { throw new AppDomainUnloadedException (); });
+		thread.Start ();
+		thread.Join ();
+	}
+
+	static int Main (string[] args)
+	{
+		ThrowTP ();
+		ThrowThread ();
+
+		return 0;
+	}
+}

mono/tests/unhandled-exception-9.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+class Driver
+{
+	/* expected exit code: 255 */
+	static void Main (string[] args)
+	{
+		if (Environment.GetEnvironmentVariable ("TEST_UNHANDLED_EXCEPTION_HANDLER") != null)
+			AppDomain.CurrentDomain.UnhandledException += (s, e) => {};
+
+		throw new AppDomainUnloadedException ();
+	}
+}