Add validation when setting linger option (#410)

***NO_CI***

Author: josesimoes

nanoFramework.System.Net/Sockets/Socket.cs

@@ -909,6 +909,12 @@ public void SetSocketOption(SocketOptionLevel optionLevel, SocketOptionName opti
                 throw new ObjectDisposedException();
             }
 
+            // Linger option requires 8 bytes (enabled flag + linger time, 4 bytes each)
+            if (optionName == SocketOptionName.Linger && optionValue.Length < 8)
+            {
+                throw new SocketException(SocketError.Fault);
+            }
+
             NativeSocket.setsockopt(this, (int)optionLevel, (int)optionName, optionValue);
         }