Annotate doc strings following r1635118.

* subversion/include/svn_client.h
  (svn_client_args_to_target_array2): Tweak to mention the release version
    as well as the revision number of the original change in v1.6.5.
  (svn_client_args_to_target_array): Document the change made in v1.6.5.

* subversion/include/svn_opt.h
  (svn_opt_parse_all_args): Document the change made in r1635118 and also
    the change made in v1.6.5.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1635151 13f79535-47bb-0310-9956-ffa450edef68