To prevent confusing / conflicting names when moving code into FSFS,
rename the fs_t struct in stats-cmd.c to query_t and the instances
from FS to QUERY.

* subversion/svnfsfs/stats-cmd.c
  (fs_t): Rename to ...
  (query_t): ... this.

  (open_rev_or_pack_file,
   get_content,
   get_cached_window,
   set_cached_window,
   fs_open,
   find_representation,
   read_rep_base,
   parse_representation,
   get_rep_content,
   read_windows,
   get_combined_window,
   read_noderev,
   parse_dir,
   read_phys_pack_file,
   read_phys_revision_file,
   read_item,
   read_log_rev_or_packfile,
   read_log_pack_file,
   read_log_revision_file,
   read_revisions): Update function signatures, rename FS to QUERY and
                    update references to QUERY.
  (subcommand__stats): Rename FS to QUERY and update references to QUERY.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1632675 13f79535-47bb-0310-9956-ffa450edef68