When running 'svn status' report externals in a deterministic way instead
of relying on the apr_hash_t ordering. Filter status in externals on the
provided changelists.

* subversion/libsvn_client/status.c
  (includes): Add svn_sorts.h.
  (do_external_status): Add changelists argument. Sort items before
    iterating over them. Pass changelist.
  (svn_client_status5): Update caller. Remove stale comment.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1550200 13f79535-47bb-0310-9956-ffa450edef68