Make 'svn update' not record a tree conflict when deleting an unmodified directory which happens to contain unversioned items. Instead, just leave the unversioned items behind on disk when deleting the unmodified directory, which matches the behaviour of Subversion 1.8.
* subversion/libsvn_wc/update_editor.c (check_tree_conflict): Ignore unversioned items during check for local mods. This prevents a tree conflict from being recorded.
* subversion/tests/cmdline/switch_tests.py (tolerate_local_mods): Don't expect an unversioned item to cause a tree conflict. Add the item to version control instead to meet this test's expectations.
* subversion/tests/cmdline/update_tests.py (update_keeps_unversioned_items_in_deleted_dir, test_list): New test which ensures that update will leave unversioned items on disk when deleting an unmodified directory.