create a directory in the backup-path area.
- Fixed a bug where make_file() was setting F_PATHNAME() on the
  receiving side.
- A non-pool (temp-memory) file structure now stores the size of
  its extra_cnt value in the F_DEPTH() int so that unmake_file()
  can always be sure of how to free() the memory.
- The ACL-preserving code no longer allocates 4 more bytes per
  file entry than it needs.
- Got rid of a useless adding of the symlink length to "bp".