Replace deprecated type exclusion in project with attribute (#394)

***NO_CI***

Author: josesimoes

nanoFramework.System.Net/NetworkHelper/IPConfiguration.cs

@@ -1,11 +1,14 @@
 // 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;
+
 namespace nanoFramework.Networking
 {
     /// <summary>
     /// IP configuration to be used for static IP address configuration.
     /// </summary>
+    [ExcludeType]
     public class IPConfiguration
     {
         /// <summary>

nanoFramework.System.Net/NetworkInformation/NetworkInformationOptions.cs

@@ -4,11 +4,14 @@
 // See LICENSE file in the project root for full license information.
 //
 
+using System.Runtime.CompilerServices;
+
 namespace System.Net.NetworkInformation
 {
     /// <summary>
     /// Options for <see cref="NetworkInformation"/>.
     /// </summary>
+    [ExcludeType]
     internal enum NetworkInformationOptions
     {
         /// <summary>

nanoFramework.System.Net/NetworkInformation/WirelessAPStation.cs

@@ -5,12 +5,14 @@
 //
 
 using System;
+using System.Runtime.CompilerServices;
 
 namespace System.Net.NetworkInformation
 {
     /// <summary>
     /// Enum of Phy protocols used for connection.
     /// </summary>
+    [ExcludeType]
     [Flags]
     public enum PhyProtocols
     {

nanoFramework.System.Net/Properties/AssemblyInfo.cs

@@ -16,7 +16,7 @@
 
 ////////////////////////////////////////////////////////////////
 // update this whenever the native assembly signature changes //
-[assembly: AssemblyNativeVersion("100.20.0.1")]
+[assembly: AssemblyNativeVersion("100.20.0.2")]
 ////////////////////////////////////////////////////////////////
 
 // Setting ComVisible to false makes the types in this assembly not visible 

nanoFramework.System.Net/Security/NetworkSecurity.cs

@@ -60,6 +60,7 @@ public enum SslProtocols
     /// <summary>
     /// The verification scheme to use for authentication.
     /// </summary>
+    [ExcludeType]
     public enum SslVerification
     {
         /// <summary>

nanoFramework.System.Net/Sockets/AddressFamily.cs

@@ -4,6 +4,8 @@
 // See LICENSE file in the project root for full license information.
 //
 
+using System.Runtime.CompilerServices;
+
 namespace System.Net.Sockets
 {
     /// <summary>
@@ -13,6 +15,7 @@ namespace System.Net.Sockets
     /// An AddressFamily member specifies the addressing scheme that a <see cref="Socket"/> will use to resolve an address. For example, 
     /// InterNetwork indicates that an IP version 4 address is expected when a <see cref="Socket"/> connects to an endpoint.
     /// </remarks>
+    [ExcludeType]
     public enum AddressFamily
     {
         /// <summary>

nanoFramework.System.Net/Sockets/ProtocolFamily.cs

@@ -4,11 +4,14 @@
 // See LICENSE file in the project root for full license information.
 //
 
+using System.Runtime.CompilerServices;
+
 namespace System.Net.Sockets
 {
     /// <summary>
     /// Specifies the type of protocol that an instance of the <see cref='Socket'/>
     /// </summary>
+    [ExcludeType]
     public enum ProtocolFamily
     {
         /// <summary>

nanoFramework.System.Net/Sockets/ProtocolType.cs

@@ -4,11 +4,14 @@
 // See LICENSE file in the project root for full license information.
 //
 
+using System.Runtime.CompilerServices;
+
 namespace System.Net.Sockets
 {
     /// <summary>
     /// Specifies the protocols that the <see cref='Socket'/> class supports.
     /// </summary>
+    [ExcludeType]
     public enum ProtocolType
     {
         /// <summary>

nanoFramework.System.Net/Sockets/SelectMode.cs

@@ -4,11 +4,14 @@
 // See LICENSE file in the project root for full license information.
 //
 
+using System.Runtime.CompilerServices;
+
 namespace System.Net.Sockets
 {
     /// <summary>
     /// Specifies the mode for polling the status of a socket.
     /// </summary>
+    [ExcludeType]
     public enum SelectMode
     {
         /// <summary>

nanoFramework.System.Net/Sockets/SocketErrors.cs

@@ -4,11 +4,14 @@
 // See LICENSE file in the project root for full license information.
 //
 
+using System.Runtime.CompilerServices;
+
 namespace System.Net.Sockets
 {
     /// <summary>
     /// Defines socket error constants.
     /// </summary>
+    [ExcludeType]
     public enum SocketError : int
     {
         /// <summary>