Add "null-info" command to svn-bench.  This simply duplicates the
info command code from the CL client and rips out all non-essential
client-side processing.

* tools/client-side/svn-bench/cl.h
  (svn_opt_subcommand_t): add null-info command

* tools/client-side/svn-bench/null-info-cmd.c
  (): new file
  (DIRENT_FIELDS,
   push_dir_info,
   client_info): duplicated and greatly simplified code from
                 client-side libs
  (svn_cl__null_info): main command implementation, does not support
                       --xml, working copy paths etc.

* tools/client-side/svn-bench/svn-bench.c
  (svn_cl__longopt_t): declare opt_changelist option
  (svn_cl__options): add description for null-info command
  (sub_main): handle new "-R" option

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1532196 13f79535-47bb-0310-9956-ffa450edef68