Add support for format7 repositories to the fsfs-stats tool.

Logically addressed revs are much easier and quicker to process
because the P2L index already contains a list of all noderevs
and change lists to read.  There is no need to read the DAG
recursively anymore (thus, no delta caching necessary etc.)

* tools/server-side/fsfs-stats.c
  (fs_open): Accept format7 repositories as well.
  (parse_representation): Don't read delta base info in log. addressing
                          mode since we can access all items directly
                          instead of discovering them in the DAG.
  (read_noderev): Same here for reading directories recursively.
  (read_pack_file): Rename to ...
  (read_phys_pack_file): ... this.
  (read_revision_file): Rename to ...
  (read_phys_revision_file): ... this.
  (read_item,
   read_log_rev_or_packfile,
   read_log_pack_file,
   read_log_revision_file): New functions to process logically addressed
                            revision contents.
  (read_revisions): Call the appropriate processing functions depending
                    on addressing mode.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1553346 13f79535-47bb-0310-9956-ffa450edef68