Extend documentation on a few new in 1.9 apis.

* subversion/include/svn_client.h
  (svn_client_cleanup2): Document several new in 1.9 arguments.
  (svn_client_cleanup): Add missing SVN_DEPRECATED.

* subversion/include/svn_wc.h
  (svn_wc_cleanup4): Document clear_dav_cache as in svn_client.h


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1604749 13f79535-47bb-0310-9956-ffa450edef68