Add <.NET 4 compatible constructor and xml doc entry to ErrorEventArgs

websocket-sharp/ErrorEventArgs.cs

@@ -49,10 +49,15 @@ namespace WebSocketSharp
 
     #region Internal Constructors
 
-    internal ErrorEventArgs (string message, Exception exc = null)
+    internal ErrorEventArgs (string message)
+      : this (message, null)
+    {
+    }
+
+    internal ErrorEventArgs (string message, Exception exception)
     {
       _message = message;
-      _exception = exc;
+      _exception = exception;
     }
 
     #endregion
@@ -72,8 +77,11 @@ namespace WebSocketSharp
     }
 
     /// <summary>
-	/// Gets the exception.
+    /// Gets the exception that caused the error.
     /// </summary>
+    /// A <see cref="Exception"/> instance that represents the cause of the error,
+    /// or <see langword="null"/> if the error isn't due to an exception.
+    /// </value>
     public Exception Exception {
       get {
         return _exception;