Remove some parameters that have long been unused.
Remove some parameters that have long been unused.

* subversion/libsvn_client/merge.c
  (get_mergeinfo_paths): Remove 'merge_src_canon_path', 'url1', 'url2',
  'revision1', 'revision2', 'ra_session'.
  (do_directory_merge): Adjust caller.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion