Fix inclusion of DefaultMemberAttribute in no reflection version (#239)

***NO_CI***

Author: josesimoes

nanoFramework.CoreLibrary/System/Reflection/DefaultMemberAttribute.cs

@@ -1,10 +1,8 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Runtime.CompilerServices;
 
-#if NANOCLR_REFLECTION
-
 namespace System.Reflection
 {
     using System;
@@ -18,17 +16,15 @@ namespace System.Reflection
     [Serializable]
     public sealed class DefaultMemberAttribute : Attribute
     {
-        private readonly String _memberName;
-
         // You must provide the name of the member, this is required
         /// <summary>
         /// Initializes a new instance of the DefaultMemberAttribute class.
         /// </summary>
         /// <param name="memberName">A String containing the name of the member to invoke. This may be a constructor, method, property, or field. 
         /// A suitable invocation attribute must be specified when the member is invoked. The default member of a class can be specified by passing an empty String as the name of the member.</param>
-        public DefaultMemberAttribute(String memberName)
+        public DefaultMemberAttribute(string memberName)
         {
-            _memberName = memberName;
+            MemberName = memberName;
         }
 
         /// <summary>
@@ -37,11 +33,6 @@ public DefaultMemberAttribute(String memberName)
         /// <value>
         /// A string representing the member name.
         /// </value>
-        public String MemberName
-        {
-            get { return _memberName; }
-        }
+        public string MemberName { get; }
     }
 }
-
-#endif // NANOCLR_REFLECTION