Fix issue #4332 as it applies to HTTPv1-speaking servers.

* subversion/libsvn_client/delete.c
  (struct repos_deletables_t): New structure for organizing stuff
    being deleted from a given repository.
  (delete_urls_multi_repos): Reorganize this function around the use
    of a single hash of struct repos_deletables_t * objects, applying
    also the following corrections/optimizations: a) use an iteration
    subpool for handling deletions associated with each repository, b)
    collapse redundant and overlapping delete targets to minimize the
    required work, and c) anchor the commit at the lowest possible
    repository directory rather than at the repository root.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1454217 13f79535-47bb-0310-9956-ffa450edef68