Stabilize Unity iOS Unit test.

Author: yfakariya

test/MsgPack.UnitTest.Xamarin.iOS/Serialization/AotTest.cs

@@ -1,4 +1,4 @@
-#region -- License Terms --
+#region -- License Terms --
 //
 // MessagePack for CLI
 //
@@ -36,6 +36,7 @@ public class AotTest
 		[TestFixtureSetUp]
 		public static void SetupFixture()
 		{
+			MessagePackSerializer.PrepareType<Timestamp>();
 			MessagePackSerializer.PrepareCollectionType<byte>();
 			MessagePackSerializer.PrepareCollectionType<char>();
 			MessagePackSerializer.PrepareCollectionType<int>();