Make the result_pool behavior of svn_wc_status3() match the documentation.

* subversion/libsvn_wc/status.c
  (get_repos_root_url_relpath,
   assemble_status): Ensure that result is fully allocated in result_pool.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1451181 13f79535-47bb-0310-9956-ffa450edef68