fts-using tools (rm, du, chmod, chgrp, chown, chcon) no longer use memory
proportional to the number of entries in each directory they process.
Before, rm -rf 4-million-entry-directory would consume about 1GiB of memory.
- Now, it uses less than 30GB, no matter how many entries there are.
+ Now, it uses less than 30MB, no matter how many entries there are.
[this bug was inherent in the use of fts: thus, for rm the bug was
introduced in coreutils-8.0. The prior implementation of rm did not use
as much memory. du, chmod, chgrp and chown started using fts in 6.0.