* Remove the SINGLEUSE feature for telldir(), it does not conform to the

* Remove the SINGLEUSE feature for telldir(), it does not conform to the
  Open Group specification.

* Add a mutex around the ddloc hash table.  Note that NetBSD implemented
  a per-dirp list but telldir/seekdir performance just isn't an issue
  for these functions so stick with the global hash table.

* Reuse the ddloc for a previous seekdir() when calling telldir() just
  after a seekdir(), instead of allocating a new one.

* rewinddir() now cleans up any ddloc's for the dirp.

Reported-by: Gary Stanley <sinknull@crater.dragonflybsd.org>