Changed beacon receiving to work in unix

Because windows and unix differ in how they handle broadcast addressing
this needs to be platform specific.  On windows any interface can
recieve broadcast by requesting to enable broadcast on the socket. On
linux to recieve broadcast you must bind to the broadcast address
specifically. Verfied using Ubuntu-16.04 mono-5.02.

src/NetMQ/NetMQBeacon.cs

@@ -5,6 +5,7 @@
 using System.Threading;
 using JetBrains.Annotations;
 using NetMQ.Sockets;
+using System.Runtime.InteropServices;
 
 namespace NetMQ
 {
@@ -105,8 +106,25 @@ private void Configure([NotNull] string interfaceName, int port)
                     {
                         if (interfaceAddress == null || @interface.Address.Equals(interfaceAddress))
                         {
-                            sendTo = @interface.BroadcastAddress;
-                            bindTo = @interface.Address;
+							// because windows and unix differ in how they handle broadcast addressing this needs to be platform specific
+							// on windows any interface can recieve broadcast by requesting to enable broadcast on the socket
+							// on linux to recieve broadcast you must bind to the broadcast address specifically
+							//bindTo = @interface.Address;
+							sendTo = @interface.BroadcastAddress;
+#if NET35 || NET40
+							if (Environment.OSVersion.Platform==PlatformID.Unix)
+#else
+							if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+#endif						
+							{
+								bindTo = @interface.BroadcastAddress;
+							}
+							else
+							{
+								bindTo = @interface.Address;
+							}
+							sendTo = @interface.BroadcastAddress;
+
                             break;
                         }
                     }
@@ -239,7 +257,7 @@ private NetMQFrame ReceiveUdpFrame(out string peerName)
             }
         }
 
-        #endregion
+#endregion
 
         private readonly NetMQActor m_actor;