Don’t loop 65536 FDs, trying to close them, when fork+exec:ing

All FDs should now have the CLOEXEC flag set, and thus there’s no
longer needed to manually loop “all” possible FDs and (trying to)
close them.

Note: the alsa module (alsalib, actually) is “racy” - while booting
up, it temporarily opens the asoundrc file without CLOEXEC. If
e.g. the script module starts its script inside this window, it’ll
have a leaked FD. Not much we can do about it though :/

Closes #169

modules/script.c

@@ -458,16 +458,6 @@ execute_script(struct module *mod)
         close(comm_pipe[1]);
         comm_pipe[1] = -1;
 
-        /* Close *all* other FDs */
-        for (int i = STDERR_FILENO + 1; i < 65536; i++) {
-            if (i == exec_pipe[1]) {
-                /* Needed for error reporting. Automatically closed
-                 * when execvp() succeeds */
-                continue;
-            }
-            close(i);
-        }
-
         execvp(m->path, argv);
 
     fail: