socket: bump listen() backlog to INT_MAX everywhere

This is a rework of #24764 by Cristian Rodríguez
<crodriguez@owncloud.com>, which stalled.

Instead of assigning -1 we'll use a macro defined to INT_MAX however.

src/libsystemd/sd-bus/test-bus-watch-bind.c

@@ -76,7 +76,7 @@ static void* thread_server(void *p) {
         assert_se(bind(fd, &u.sa, sa_len) >= 0);
         usleep(100 * USEC_PER_MSEC);
 
-        assert_se(listen(fd, SOMAXCONN) >= 0);
+        assert_se(listen(fd, SOMAXCONN_DELUXE) >= 0);
         usleep(100 * USEC_PER_MSEC);
 
         assert_se(touch(path) >= 0);