Added NetConnection.CanSendImmediately() to determine if the sliding window is full

Recycle outgoing dropped messages
Encryption using CryptoProviders refactored 
Added NetUnreliableSizeBehaviour to configure behaviour for unreliable messages above MTU
Debug stats show number of received fragments

Lidgren.Network/Encryption/NetEncryption.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Security.Cryptography;
 
 namespace Lidgren.Network
 {
@@ -23,6 +24,14 @@ namespace Lidgren.Network
 			m_peer = peer;
 		}
 
+		public void SetKey(string str)
+		{
+			var bytes = System.Text.Encoding.ASCII.GetBytes(str);
+			SetKey(bytes, 0, bytes.Length);
+		}
+
+		public abstract void SetKey(byte[] data, int offset, int count);
+
 		/// <summary>
 		/// Encrypt an outgoing message in place
 		/// </summary>