The optional lecture file is left open and passed to the target program, at
least in the case of "sudo su" on HP-UX 11.00. This is a problem if lecture is
on a file system I later need to unmount without disturbing the program launched
by sudo. Looks like check.c needs an fclose after line 131 (1.6.8p12).

    if (def_lecture_file && (fp = fopen(def_lecture_file, "r")) != NULL) {
        while ((nread = fread(buf, sizeof(char), sizeof(buf), fp)) != 0)
            fwrite(buf, nread, 1, stderr);
# next line is proposed addition
        fclose(fp);
    } else {