Prepare 'svnfsfs stats' code to be split into a logic part within FSFS,
a UI bit in svnfsfs and an FSFS-private interface in between them.

This patch moves all stats information from the fs_t struct and function
locals into a separate svn_fs_fs__stats_t struct.  All field types in that
struct are renamed to svn_fs_fs__*.  No code is being moved outside the
original file, yet.

* subversion/svnfsfs/stats-cmd.c
  (large_change_info_t,
   largest_changes_t,
   histogram_line_t, 
   histogram_t,
   extension_info_t,
   rep_pack_stats_t,
   representation_stats_t,
   node_stats_t): Put these into one location and rename them to ...
  (svn_fs_fs__large_change_info_t,
   svn_fs_fs__largest_changes_t,
   svn_fs_fs__histogram_line_t,
   svn_fs_fs__histogram_t,
   svn_fs_fs__extension_info_t,
   svn_fs_fs__rep_pack_stats_t,
   svn_fs_fs__representation_stats_t,
   svn_fs_fs__node_stats_t): ... these.  Update members that have
                             renamed types.
  (svn_fs_fs__stats_t): The new stats main struct. Members are taken
                        from fs_t or are formaer print_stats() locals.
  (fs_t): Update to use a svn_fs_fs__stats_t instance now.

  (initialize_largest_changes): Take the new stats type as parameter
                                instead of the fs_t.
  (add_to_histogram): Update signature due to type rename.
  (add_change): Take the new stats type as parameter instead of the fs_t.
  (read_noderev): Update caller.
  (read_revisions): Update initialization.

  (add_rep_pack_stats,
   add_rep_stats,
   print_rep_stats,
   print_largest_reps,
   print_histogram): Update signature due to type rename.
  (compare_count,
   compare_node_size,
   compare_rep_size,
   merge_by_extension): Update local variable type names.

  (get_by_extensions,
   print_extensions_by_changes,
   print_extensions_by_nodes,
   print_extensions_by_reps,
   print_histograms_by_extension): Use stats instead of fs in the signature
                                   and update the code due to type renames.
  (aggregate_stats): New function that contains the data aggregation logic
                     previously found in print_stats().
  (print_stats): Take an stats struct instead of fs_t and just display its
                 contents.
  (subcommand__stats): Update caller.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1632450 13f79535-47bb-0310-9956-ffa450edef68