Change MaxDepth default to 64 (#2473)

Src/Newtonsoft.Json.Tests/Serialization/JsonSerializerTest.cs

@@ -8000,10 +8000,10 @@ This is just junk, though.";
         public void SetMaxDepth_DepthExceeded()
         {
             JsonTextReader reader = new JsonTextReader(new StringReader("[[['text']]]"));
-            Assert.AreEqual(128, reader.MaxDepth);
+            Assert.AreEqual(64, reader.MaxDepth);
 
             JsonSerializerSettings settings = new JsonSerializerSettings();
-            Assert.AreEqual(128, settings.MaxDepth);
+            Assert.AreEqual(64, settings.MaxDepth);
             Assert.AreEqual(false, settings._maxDepthSet);
 
             // Default should be the same
@@ -8034,7 +8034,7 @@ This is just junk, though.";
 
             serializer.Deserialize(reader);
 
-            Assert.AreEqual(128, reader.MaxDepth);
+            Assert.AreEqual(64, reader.MaxDepth);
         }
     }
 }

Src/Newtonsoft.Json/JsonReader.cs

@@ -329,7 +329,7 @@ namespace Newtonsoft.Json
             _dateTimeZoneHandling = DateTimeZoneHandling.RoundtripKind;
             _dateParseHandling = DateParseHandling.DateTime;
             _floatParseHandling = FloatParseHandling.Double;
-            _maxDepth = 128;
+            _maxDepth = 64;
 
             CloseInput = true;
         }

Src/Newtonsoft.Json/JsonSerializerSettings.cs

@@ -61,7 +61,7 @@ namespace Newtonsoft.Json
         internal static readonly CultureInfo DefaultCulture;
         internal const bool DefaultCheckAdditionalContent = false;
         internal const string DefaultDateFormatString = @"yyyy'-'MM'-'dd'T'HH':'mm':'ss.FFFFFFFK";
-        internal const int DefaultMaxDepth = 128;
+        internal const int DefaultMaxDepth = 64;
 
         internal Formatting? _formatting;
         internal DateFormatHandling? _dateFormatHandling;