Apply tweaked version of stsp's patch resolving issue #4531. This patch adds
proper scratch pool handling over the recursive resource walking in mod_dav.

This walker is used for many recursive operations initiated by mod_dav, most
importantly for testing authz and locks. Before this patch the entries of all
directories walked were stored in the single request pool.

* subversion/mod_dav_svn/repos.c
  (do_walk): Add scratch_pool argument. Use this to store temporary data.
    Pass iterpool as scratch pool on recursion.
  (walk): Update caller.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1643810 13f79535-47bb-0310-9956-ffa450edef68