Avoid socket handle leakage on Unix

Source/Native/enet.h

@@ -4565,7 +4565,7 @@ extern "C" {
 		}
 
 		ENetSocket enet_socket_create(ENetSocketType type) {
-			return socket(PF_INET6, type == ENET_SOCKET_TYPE_DATAGRAM ? SOCK_DGRAM : SOCK_STREAM, 0);
+			return socket(PF_INET6, (type == ENET_SOCKET_TYPE_DATAGRAM ? SOCK_DGRAM : SOCK_STREAM) | SOCK_CLOEXEC, 0);
 		}
 
 		int enet_socket_set_option(ENetSocket socket, ENetSocketOption option, int value) {
@@ -5162,4 +5162,4 @@ extern "C" {
 }
 #endif
 #endif
-#endif
+#endif