savedir: add sorting arg to savedir, streamsavedir; remove fdsavedir Patch based on an idea by Dick Streefland in <https://savannah.gnu.org/patch/?7892>. * NEWS: Document this. * lib/savedir.c (NAME_SIZE_DEFAULT): Remove. (direntry_t, comparison_function): New types. (direntry_cmp_name): New function. (direntry_cmp_inode) [D_INO_IN_DIRENT]: New function. (streamsavedir, savedir): New arg OPTION. (streamsavedir): Simplify memory allocation. (fdsavedir): Remove. * lib/savedir.h (enum savedir_option): New type. (streamsavedir, savedir): New arg OPTION. (fdsavedir): Remove.