Add check for SO_REUSEPORT

Fixes #51

edge_utils.c

@@ -1747,8 +1747,8 @@ int quick_edge_init(char *device_name, char *community_name,
     
     /* allow multiple sockets to use the same PORT number */
     setsockopt(eee.udp_multicast_sock, SOL_SOCKET, SO_REUSEADDR, &enable_reuse, sizeof(enable_reuse));
-#ifndef WIN32 /* no SO_REUSEPORT in Windows */
-	  setsockopt(eee.udp_multicast_sock, SOL_SOCKET, SO_REUSEPORT, &enable_reuse, sizeof(enable_reuse));
+#ifdef SO_REUSEPORT /* no SO_REUSEPORT in Windows / old linux versions */
+    setsockopt(eee.udp_multicast_sock, SOL_SOCKET, SO_REUSEPORT, &enable_reuse, sizeof(enable_reuse));
 #endif
 
     mreq.imr_multiaddr.s_addr = inet_addr(N2N_MULTICAST_GROUP);