Make the fsfs-stats tool code compatible with the FSFS lib such that
we may reuse code from the latter instead of reimplementing it.

Simply rename tool-specific data structs to make them no longer
clash with FSFS data types.

* tools/server-side/fsfs-stats.c
  (representation_t): Rename to ...
  (rep_stats_t): ... this.
  (window_cache_key_t): Rename to ...
  (cache_key_t): ... this.
  (fs_fs_t): Rename to ...
  (fs_t): ... this.
  (*): Global search & replace of the above.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1553335 13f79535-47bb-0310-9956-ffa450edef68