-Added Portable Class Library build

Src/Newtonsoft.Json/JsonSerializationException.cs

@@ -33,7 +33,7 @@ namespace Newtonsoft.Json
   /// <summary>
   /// The exception thrown when an error occurs during Json serialization or deserialization.
   /// </summary>
-#if !(SILVERLIGHT || WINDOWS_PHONE || NETFX_CORE)
+#if !(SILVERLIGHT || WINDOWS_PHONE || NETFX_CORE || PORTABLE)
   [Serializable]
 #endif
   public class JsonSerializationException : Exception
@@ -66,7 +66,7 @@ namespace Newtonsoft.Json
     {
     }
 
-#if !(WINDOWS_PHONE || SILVERLIGHT || NETFX_CORE)
+#if !(WINDOWS_PHONE || SILVERLIGHT || NETFX_CORE || PORTABLE)
     /// <summary>
     /// Initializes a new instance of the <see cref="JsonSerializationException"/> class.
     /// </summary>