glob, backupfile: inode 0 is a valid inode number * doc/posix-functions/readdir.texi (readdir): * doc/posix-headers/dirent.texi (dirent.h): Document more readdir portability issues. * lib/backupfile.c (REAL_DIR_ENTRY): Remove. (numbered_backup): Don’t treat inode 0 any differently from other inode values. * lib/glob.c (struct readdir_result): Remove skip_entry member. (readdir_result_skip_entry, D_INO_TO_RESULT): Remove. All uses removed. * modules/glob (Depends-on): Remove d-ino.