Continue work on svn_fs_fs__get_stats API.  We must redirect the progress
output to a progress callback.

* subversion/svnfsfs/stats-cmd.c
  (query_t): Add progress callback members.
  (print_progress): Remove the old implemenation.

  (read_phys_pack_file,
   read_phys_revision_file,
   read_log_pack_file,
   read_log_revision_file): Invoke progress callback instead of a local
                            print function.

  (create_query): Store the callback in the query struct.
  (svn_fs_fs__get_stats): Add progress callback parameters.

  (print_progress): Reimplement with callback interface.
  (subcommand__stats): Update API caller.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1632689 13f79535-47bb-0310-9956-ffa450edef68