Windows: Use SO_EXCLUSIVEADDRUSE flag for IPC socket

SO_REUSEADDR on Windows allows to bind to an already used port
without an error. This way we never notice if the port is already used.
So use the Windows special flag SO_EXCLUSIVEADDRUSE to ensure we receive
an error if the port is already used.

Part of #641.

src/socket.c

@@ -524,7 +524,7 @@ static gint socket_fd_open_inet(gushort port)
 	}
 
 	val = 1;
-	if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)) < 0)
+	if (setsockopt(sock, SOL_SOCKET, SO_EXCLUSIVEADDRUSE, &val, sizeof(val)) < 0)
 	{
 		log_error("Failed to set IPC socket exclusive option", -1);
 		socket_fd_close(sock);